@article{
 title = {Crack propagation mechanism of smooth blasting holes for tunnel excavation under high in-situ stress},
 type = {article},
 year = {2024},
 keywords = {Crack propagation,Crush zone,FDEM,High in-situ stress,Smooth blasting},
 pages = {110144},
 volume = {304},
 publisher = {Elsevier},
 id = {3507efd4-8411-3e07-9b85-759b04104ed0},
 created = {2025-04-14T02:52:45.010Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2025-04-14T02:52:45.010Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 source_type = {JOUR},
 private_publication = {false},
 abstract = {Smooth blasting is an important excavation method in tunnel construction, creating a smooth and even excavation profile during the excavation process. In this study, the influence of in-situ stress, hole spacing, and radial decoupling coefficient on the superposition of blasting stress and the cracking characteristic between holes were investigated by using integrated analytical and numerical analyses (FDEM). Based on those results, the design of smooth blasting parameters considering the influence of in-situ stress were suggested, and verified against the data collected during the blasting excavation of diversion tunnel at Jinping II hydropower station. The results indicated that the propagation of blast-induced fractures are significantly influenced by the insitu stress conditions, tending to extend towards the direction of the maximum principal stress thus the holes should be arranged along the direction of the maximum principal stress to ensure the formation of cracks between holes and smooth excavation of the wall.},
 bibtype = {article},
 author = {Lu, Ang and Yan, Peng and Lu, Wenbo and Li, Xiaofeng and Liu, Xiao and Luo, Sheng and Huang, Shuling and Grasselli, Giovanni},
 doi = {10.1016/j.engfracmech.2024.110144},
 journal = {Engineering Fracture Mechanics}
}

Smooth blasting is an important excavation method in tunnel construction, creating a smooth and even excavation profile during the excavation process. In this study, the influence of in-situ stress, hole spacing, and radial decoupling coefficient on the superposition of blasting stress and the cracking characteristic between holes were investigated by using integrated analytical and numerical analyses (FDEM). Based on those results, the design of smooth blasting parameters considering the influence of in-situ stress were suggested, and verified against the data collected during the blasting excavation of diversion tunnel at Jinping II hydropower station. The results indicated that the propagation of blast-induced fractures are significantly influenced by the insitu stress conditions, tending to extend towards the direction of the maximum principal stress thus the holes should be arranged along the direction of the maximum principal stress to ensure the formation of cracks between holes and smooth excavation of the wall.

@article{
 title = {Rate-dependent strength and crack damage thresholds of rocks at intermediate strain rate},
 type = {article},
 year = {2023},
 keywords = {Confining p,Servo-controlled apparatus,Strain rate,servo-controlled apparatus},
 pages = {105590},
 volume = {171},
 websites = {https://linkinghub.elsevier.com/retrieve/pii/S1365160923002642},
 month = {11},
 publisher = {Elsevier Ltd},
 id = {6cdb894d-e143-3228-99f9-301283cafdb3},
 created = {2023-10-11T09:28:41.819Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2023-10-12T03:03:45.446Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {false},
 hidden = {false},
 private_publication = {false},
 bibtype = {article},
 author = {Li, Haibo and Liu, Liwang and Fu, Shuaiyang and Liu, Bo and Li, Xiaofeng},
 doi = {10.1016/j.ijrmms.2023.105590},
 journal = {International Journal of Rock Mechanics and Mining Sciences},
 number = {July 2022}
}

@article{
 title = {A benchmark study of different numerical methods for predicting rock failure},
 type = {article},
 year = {2023},
 keywords = {Benchmark,Numerical methods,Parameter calibration,Rock failure},
 pages = {105381},
 volume = {166},
 month = {6},
 publisher = {Elsevier Ltd},
 id = {f4913da6-81bd-35ff-9efc-64bfd3a78d61},
 created = {2023-10-11T09:54:13.500Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2023-10-12T03:03:45.482Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Li2023},
 private_publication = {false},
 abstract = {Nowadays, with many available numerical methods developed in rock mechanics, researchers have always focused on the parameter calibration of the numerical model but ignored the predictive capability of these methods. A comparative study of nine commonly used numerical methods was performed for predicting rock failure through international cooperation organized by the Discontinuous Deformation Analysis (DDA) commission of the International Society for Rock Mechanics (ISRM). Two steps of numerical modelling were conducted including a calibration procedure from given experimental results and a numerical prediction for benchmark tests with these calibrated parameters for three types of rocks. Through the comparison between different numerical and experimental results, the inherent weaknesses and strengths of different numerical methods in terms of predicting rock failure were identified and analysed. The influence of human intervention in terms of parameter selection is even more significant than the choice of different numerical methods. Some potential factors (i.e., different boundary conditions, heterogeneity of rock material, strength parameters, particle packing, and failure criteria) that may occur in numerical and physical tests were further discussed. Through the comparison of different failure criteria, we found the selection of rock failure criterion might be the major factor that affected the predictive capability of numerical methods, and the nonlinear failure model (the Hoek–Brown criterion) showed the superiority in the prediction of rock fracturing subjected to complex stress conditions. This comparative work also enlightens the significance of a high-quality calibration process and the future advancement of rock failure criteria.},
 bibtype = {article},
 author = {Li, Yi-Ming and Zhao, Gao-Feng and Jiao, Yuyong and Yan, Chengzeng and Wang, Xun and Shen, Luming and Yang, Lei and Liang, Zhengzhao and Li, Wanrun and Zhou, Xiaoxiong and Li, Xiaofeng and Liu, Feng and Zhang, Kaiyu and Li, Xing and Pan, Cheng and Le, Tiancheng},
 doi = {10.1016/j.ijrmms.2023.105381},
 journal = {International Journal of Rock Mechanics and Mining Sciences},
 number = {February}
}

Nowadays, with many available numerical methods developed in rock mechanics, researchers have always focused on the parameter calibration of the numerical model but ignored the predictive capability of these methods. A comparative study of nine commonly used numerical methods was performed for predicting rock failure through international cooperation organized by the Discontinuous Deformation Analysis (DDA) commission of the International Society for Rock Mechanics (ISRM). Two steps of numerical modelling were conducted including a calibration procedure from given experimental results and a numerical prediction for benchmark tests with these calibrated parameters for three types of rocks. Through the comparison between different numerical and experimental results, the inherent weaknesses and strengths of different numerical methods in terms of predicting rock failure were identified and analysed. The influence of human intervention in terms of parameter selection is even more significant than the choice of different numerical methods. Some potential factors (i.e., different boundary conditions, heterogeneity of rock material, strength parameters, particle packing, and failure criteria) that may occur in numerical and physical tests were further discussed. Through the comparison of different failure criteria, we found the selection of rock failure criterion might be the major factor that affected the predictive capability of numerical methods, and the nonlinear failure model (the Hoek–Brown criterion) showed the superiority in the prediction of rock fracturing subjected to complex stress conditions. This comparative work also enlightens the significance of a high-quality calibration process and the future advancement of rock failure criteria.

@article{
 title = {全伺服式中等应变率三轴试验系统的研制及应用},
 type = {article},
 year = {2022},
 pages = {480},
 id = {dc00d5fc-c69e-362b-93dc-67fa43c692a8},
 created = {2021-12-05T04:02:13.793Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2023-10-12T02:55:28.218Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {2022},
 source_type = {JOUR},
 private_publication = {false},
 bibtype = {article},
 author = {李海波, undefined and 刘黎旺, undefined and 李晓锋, undefined and 刘博, undefined and 李俊如, undefined},
 journal = {岩石力学与工程学报}
}

@article{
 title = {Measurement of ejection velocity of rock fragments under dynamic compression and insight into energy partitioning},
 type = {article},
 year = {2022},
 keywords = {3D digital image correlation,Dynamic compression,Ejection velocity,Energy partitioning,Rock fragmentation},
 pages = {104992},
 volume = {149},
 month = {1},
 publisher = {Elsevier Ltd},
 id = {57988c10-0394-38a4-ac3e-c8551531b5af},
 created = {2021-12-05T04:02:13.796Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2025-03-13T09:07:00.707Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Xing2022},
 private_publication = {false},
 abstract = {High-speed three-dimensional digital image correlation (3D-DIC) technique was utilised to examine the ejection velocity characteristics of rock fragment in dynamic compression tests. The fragment velocity components of fragment were extracted from velocity fields distributed within the fragment area. By identifying the peak resultant velocity, the initial fragment ejection velocity was determined. The kinetic energy of fragments was evaluated with the initial ejection velocity and the mass of the fragments in each size group. Results show that the fragment movement is successively accelerated by stress-wave propagation, crack opening and Poisson's effect which contribute to the axial, circumferential and radial velocity component of fragment, respectively. The variance in circumferential velocity of two neighbouring fragment areas indicates the formation of fragments. The peak value of radial velocity, which is the chief component in ejection velocity reveals the time when ejection taking place. The initial ejection velocity of fragment gradually decreases with increasing size, but increases significantly as strain rate increases. The kinetic energy of fragments ejection comprises 12%∼24% of absorbed energy at strain rate of 69∼100 s-1, and the percentage further increases with increasing strain rates. Ignoring the kinetic energy of fragments will lead to overestimation of dissipated energy consumed by rock fragmentation in dynamic compression.},
 bibtype = {article},
 author = {Xing, Haozhe and Wang, Mingyang and Ju, Minghe and Li, Jianchun and Li, Xiaofeng},
 doi = {10.1016/j.ijrmms.2021.104992},
 journal = {International Journal of Rock Mechanics and Mining Sciences}
}

High-speed three-dimensional digital image correlation (3D-DIC) technique was utilised to examine the ejection velocity characteristics of rock fragment in dynamic compression tests. The fragment velocity components of fragment were extracted from velocity fields distributed within the fragment area. By identifying the peak resultant velocity, the initial fragment ejection velocity was determined. The kinetic energy of fragments was evaluated with the initial ejection velocity and the mass of the fragments in each size group. Results show that the fragment movement is successively accelerated by stress-wave propagation, crack opening and Poisson's effect which contribute to the axial, circumferential and radial velocity component of fragment, respectively. The variance in circumferential velocity of two neighbouring fragment areas indicates the formation of fragments. The peak value of radial velocity, which is the chief component in ejection velocity reveals the time when ejection taking place. The initial ejection velocity of fragment gradually decreases with increasing size, but increases significantly as strain rate increases. The kinetic energy of fragments ejection comprises 12%∼24% of absorbed energy at strain rate of 69∼100 s-1, and the percentage further increases with increasing strain rates. Ignoring the kinetic energy of fragments will lead to overestimation of dissipated energy consumed by rock fragmentation in dynamic compression.

@article{
 title = {A review of the effects of weak interfaces on crack propagation in rock: from phenomenon to mechanism},
 type = {article},
 year = {2022},
 keywords = {Crack deflection criterion,Crack propagation,Dynamic loading,Heterogeneous rock,Weak interface},
 pages = {108297},
 volume = {263},
 month = {3},
 publisher = {Elsevier Ltd},
 id = {eaebfe6b-055d-3177-b60e-b5c4a60ccdc6},
 created = {2022-02-23T16:48:48.297Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2023-10-12T02:55:29.437Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Ju2022},
 private_publication = {false},
 bibtype = {article},
 author = {Ju, Minghe and Li, Xiaofeng and Li, Xing and Zhang, Guanglei},
 doi = {10.1016/j.engfracmech.2022.108297},
 journal = {Engineering Fracture Mechanics},
 number = {September 2021}
}

@article{
 title = {Application of a synthetic rock mass approach to the simulation of blasting-induced crack propagation and coalescence in deep fractured rock},
 type = {article},
 year = {2022},
 pages = {57},
 volume = {8},
 month = {4},
 day = {15},
 id = {86d39854-f195-383e-936b-c12dad970589},
 created = {2022-03-15T19:30:55.152Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2022-03-15T19:30:55.152Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Li2022},
 source_type = {JOUR},
 private_publication = {false},
 abstract = {As the excavation depth of underground engineering increases, the influence of in situ stress on the blasting effect cannot be ignored. The large number of fractures in the natural rock mass, coupled with the in situ stress, significantly impacts the propagation of stress waves. In this research, a synthetic rock mass approach based on the UDEC grain-based model was employed to investigate crack propagation and coalescence during double-borehole blasting with a variety of fracture networks and in situ stress conditions. The effects of the buried depth, fracture geometric parameters (i.e., the length and intensity), blast parameters (i.e., the explosive charge and borehole spacing), and borehole layouts on blasting-induced rock fracturing were examined. The simulation results showed that for a low-density fracture network dominated by short fractures, the pre-existing fractures have little effect on the propagation of blasting-induced cracks. However, as the length or density of fractures increases, pre-existing fractures could restrain the blasting-induced radial crack propagation and enhance the rock fragmentation between the borehole and the pre-existing fracture. This effect gradually disappeared as the in situ stress increased. In addition, the mismatch between the centreline of double boreholes and the direction of high in situ stress could also affect the coalescence of cracks, especially in high-density fracture networks. Finally, the applicability of empty holes to improve the crack coalescence between boreholes in fractured rock was discussed. This study should be beneficial in understanding the blasting behaviour of deep fractured rocks.},
 bibtype = {article},
 author = {Li, Xing and Pan, Cheng and Li, Xiaofeng and Shao, Chengmeng and Li, Haibo},
 doi = {10.1007/s40948-022-00376-4},
 journal = {Geomechanics and Geophysics for Geo-Energy and Geo-Resources},
 number = {2}
}

As the excavation depth of underground engineering increases, the influence of in situ stress on the blasting effect cannot be ignored. The large number of fractures in the natural rock mass, coupled with the in situ stress, significantly impacts the propagation of stress waves. In this research, a synthetic rock mass approach based on the UDEC grain-based model was employed to investigate crack propagation and coalescence during double-borehole blasting with a variety of fracture networks and in situ stress conditions. The effects of the buried depth, fracture geometric parameters (i.e., the length and intensity), blast parameters (i.e., the explosive charge and borehole spacing), and borehole layouts on blasting-induced rock fracturing were examined. The simulation results showed that for a low-density fracture network dominated by short fractures, the pre-existing fractures have little effect on the propagation of blasting-induced cracks. However, as the length or density of fractures increases, pre-existing fractures could restrain the blasting-induced radial crack propagation and enhance the rock fragmentation between the borehole and the pre-existing fracture. This effect gradually disappeared as the in situ stress increased. In addition, the mismatch between the centreline of double boreholes and the direction of high in situ stress could also affect the coalescence of cracks, especially in high-density fracture networks. Finally, the applicability of empty holes to improve the crack coalescence between boreholes in fractured rock was discussed. This study should be beneficial in understanding the blasting behaviour of deep fractured rocks.

@article{
 title = {THE 2022 ISRM ROCHA MEDAL Coupled Experimental and Numerical Investigations on Rock Fracturing and Fragmentation Subject to Impact Loading},
 type = {article},
 year = {2022},
 pages = {1-46},
 id = {be1d483f-6f65-3b64-9232-651336fcbd07},
 created = {2022-06-20T19:20:52.416Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2023-10-12T02:55:29.537Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {false},
 hidden = {false},
 private_publication = {false},
 bibtype = {article},
 author = {Li, Xiaofeng}
}

@article{
 title = {A state-of-the-art review of mechanical characteristics and cracking processes of pre-cracked rocks under quasi-static compression},
 type = {article},
 year = {2022},
 keywords = {Crack coalescence pattern,Crack initiation pattern,Failure pattern,Pre-cracked rock},
 pages = {2034-2057},
 volume = {14},
 month = {12},
 publisher = {Institute of Rock and Soil Mechanics, Chinese Academy of Sciences},
 id = {b06ebc9c-dd55-376b-bcd4-3386f6924bb6},
 created = {2022-06-20T19:20:52.417Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2023-10-12T02:55:29.785Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Liu2022},
 private_publication = {false},
 abstract = {The mechanical characteristics and failure behavior of rocks containing flaws or discontinuities have received wide attention in the field of rock mechanics. When external loads are applied to rock materials, stress-induced cracks would initiate and propagate from the flaws, ultimately leading to the irreversible failure of rocks. To investigate the cracking behavior and the effect of flaw geometries on the mechanical properties of rock materials, a series of samples containing one, two and multiple flaws have been widely investigated in the laboratory. In this paper, the experimental results for pre-cracked rocks under quasi-static compression were systematically reviewed. The progressive failure process of intact rocks is briefly described to reveal the background for experiments on samples with flaws. Then, the nondestructive measurement techniques utilized in experiments, such as acoustic emission (AE), X-ray computed tomography (CT), and digital image correlation (DIC), are summarized. The mechanical characteristics of rocks with different flaw geometries and under different loading conditions, including the geometry of pre-existing flaws, flaw filling condition and confining pressure, are discussed. Furthermore, the cracking process is evaluated from the perspective of crack initiation, coalescence, and failure patterns.},
 bibtype = {article},
 author = {Liu, Liwang and Li, Haibo and Li, Xiaofeng},
 doi = {10.1016/j.jrmge.2022.03.013},
 journal = {Journal of Rock Mechanics and Geotechnical Engineering},
 number = {6}
}

The mechanical characteristics and failure behavior of rocks containing flaws or discontinuities have received wide attention in the field of rock mechanics. When external loads are applied to rock materials, stress-induced cracks would initiate and propagate from the flaws, ultimately leading to the irreversible failure of rocks. To investigate the cracking behavior and the effect of flaw geometries on the mechanical properties of rock materials, a series of samples containing one, two and multiple flaws have been widely investigated in the laboratory. In this paper, the experimental results for pre-cracked rocks under quasi-static compression were systematically reviewed. The progressive failure process of intact rocks is briefly described to reveal the background for experiments on samples with flaws. Then, the nondestructive measurement techniques utilized in experiments, such as acoustic emission (AE), X-ray computed tomography (CT), and digital image correlation (DIC), are summarized. The mechanical characteristics of rocks with different flaw geometries and under different loading conditions, including the geometry of pre-existing flaws, flaw filling condition and confining pressure, are discussed. Furthermore, the cracking process is evaluated from the perspective of crack initiation, coalescence, and failure patterns.

@article{
 title = {Modelling of gas-driven fracturing and fragmentation in liquid CO2 blasting using finite-discrete element method},
 type = {article},
 year = {2022},
 keywords = {"CO2 blasting,Fragmentation,Rock breakage,The combined finite-discrete element method,co 2 blasting,gas penetration,gas penetration",method,the combined finite-discrete element},
 pages = {409-421},
 volume = {144},
 month = {11},
 publisher = {Elsevier Ltd},
 id = {3ad5cc9f-c5a4-3714-8d4b-755b5f8fa6ce},
 created = {2022-09-06T20:36:33.380Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2023-10-12T02:55:29.610Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {false},
 hidden = {false},
 private_publication = {false},
 bibtype = {article},
 author = {Wang, Ben and Li, Haibo and Xing, Haozhe and Li, Xiaofeng},
 doi = {10.1016/j.enganabound.2022.08.041},
 journal = {Engineering Analysis with Boundary Elements},
 number = {September}
}

@article{
 title = {基于 DIC 方法与声发射的花岗岩断裂 过程区范围研究},
 type = {article},
 year = {2022},
 keywords = {acoustic emission,crack opening,digital image correlation,displacement,fracture process zone,granite,rock mechanics},
 volume = {41},
 id = {d141ef68-91c8-3a8a-85c0-3dc3bff02de6},
 created = {2022-09-06T20:36:33.387Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2023-10-12T02:55:29.819Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {false},
 hidden = {false},
 private_publication = {false},
 bibtype = {article},
 author = {傅帅旸;李海波;李晓锋;, undefined},
 number = {2020}
}

@article{
 title = {粒子重复冲击破岩细观损伤及破碎特征试验研究},
 type = {article},
 year = {2022},
 pages = {1-13},
 id = {d836cbad-71dd-39e7-a7f3-caf5dd30dd8a},
 created = {2022-12-16T19:28:54.965Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2023-10-12T02:55:29.688Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {false},
 hidden = {false},
 private_publication = {false},
 abstract = {粒子冲击破岩作为一种新型辅助破岩技术已于钻探和油气开采等领域得到有效运用，其在极坚硬岩层中隧（巷）道辅助掘进方面具有广阔的应用前景。笔者从实验角度研究了粒子的冲击次数、颗粒强度及冲击速度等因素对极坚硬花岗岩表面冲击坑损伤破碎特征的影响，对冲击坑三维形貌、岩石碎屑及坑内矿物破碎特征进行了定量分析。结果表明：成坑最大深度随冲击次数增加呈抛物线趋势增大，而成坑体积和坑顶面积随冲击次数增加呈线性增长；成坑体积随冲击速度呈先增大后减小的规律，针对本文工况该临界冲击速度约为82.5 m/s；冲击坑中心与外部的细观破碎机理差异导致岩石碎屑平均尺寸具有明显的双峰特征。从能量角度分析发现，成坑体积、坑顶面积和最大深度随粒子动能在双对数坐标系下线性增长。基于图像处理方法获得了冲击坑周边主要矿物内部裂纹分布随冲击速度和次数增加的分形维数变化规律，破岩效果表明增大粒子冲击速度和冲击次数能有效扩大岩石冲击坑的损伤范围，但冲击速度的影响程度显著大于冲击次数。},
 bibtype = {article},
 author = {鞠明和;陶泽军;李晓锋;蔚立元;姜礼杰;李晓昭;, undefined},
 doi = {10.16285/j.rsm.2022.0039},
 journal = {岩土力学},
 number = {12}
}

粒子冲击破岩作为一种新型辅助破岩技术已于钻探和油气开采等领域得到有效运用，其在极坚硬岩层中隧（巷）道辅助掘进方面具有广阔的应用前景。笔者从实验角度研究了粒子的冲击次数、颗粒强度及冲击速度等因素对极坚硬花岗岩表面冲击坑损伤破碎特征的影响，对冲击坑三维形貌、岩石碎屑及坑内矿物破碎特征进行了定量分析。结果表明：成坑最大深度随冲击次数增加呈抛物线趋势增大，而成坑体积和坑顶面积随冲击次数增加呈线性增长；成坑体积随冲击速度呈先增大后减小的规律，针对本文工况该临界冲击速度约为82.5 m/s；冲击坑中心与外部的细观破碎机理差异导致岩石碎屑平均尺寸具有明显的双峰特征。从能量角度分析发现，成坑体积、坑顶面积和最大深度随粒子动能在双对数坐标系下线性增长。基于图像处理方法获得了冲击坑周边主要矿物内部裂纹分布随冲击速度和次数增加的分形维数变化规律，破岩效果表明增大粒子冲击速度和冲击次数能有效扩大岩石冲击坑的损伤范围，但冲击速度的影响程度显著大于冲击次数。

@article{
 title = {《岩土力学》网络首发论文},
 type = {article},
 year = {2022},
 id = {21ad7ba1-0d7f-35ae-bbba-cb47f583f0ed},
 created = {2023-10-11T09:54:13.387Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2023-10-12T02:55:30.972Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {false},
 hidden = {false},
 private_publication = {false},
 bibtype = {article},
 author = {Mechanics, Soil}
}

@article{
 title = {Underlying Mechanisms of Crack Initiation for Granitic Rocks Containing a Single Pre-existing Flaw: Insights From Digital Image Correlation (DIC) Analysis},
 type = {article},
 year = {2021},
 keywords = {Anti-wing cracks,Crack initiation mechanisms,Digital image correlation (DIC) analysis,Pre-existing flaw,Wing cracks},
 pages = {857-873},
 volume = {54},
 month = {11},
 id = {ccf0c58f-98cf-3944-b2c1-06282958815a},
 created = {2020-12-17T11:18:02.641Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2021-11-14T01:17:49.845Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Liu2020e},
 private_publication = {false},
 abstract = {Determination on underlying mechanisms of crack initiation is of vital importance to understand the failure processes of geomaterials in practical engineering. In this study, uniaxial compression experiments of granitic samples containing a single pre-existing flaw were conducted and the failure processes were recorded by using the high-speed camera. To quantitatively determine the crack initiation mechanism, a novel method was first proposed based on digital image correlation (DIC) analysis and then its validity was confirmed. By utilizing this method, three types of cracks with different initiation mechanisms were identified and the effect of flaw inclination angle on crack initiation mechanisms was discussed from the viewpoint of theoretical analysis. With the increase of inclination angles, wing cracks change from mixed mode I/II cracks to mode I cracks, while anti-wing cracks have no evident changes and are dominated by mode II cracks. Under compressive pressure, the upper and bottom surfaces of pre-existing flaw deform to each other and the distributions of full-field tangential stress around flaw are different, which might induce the variation of crack initiation mechanisms with regard to the inclination angle.},
 bibtype = {article},
 author = {Liu, Liwang and Li, Haibo and Li, Xiaofeng and Wu, Di and Zhang, Guokai},
 doi = {10.1007/s00603-020-02286-x},
 journal = {Rock Mechanics and Rock Engineering},
 number = {2}
}

Determination on underlying mechanisms of crack initiation is of vital importance to understand the failure processes of geomaterials in practical engineering. In this study, uniaxial compression experiments of granitic samples containing a single pre-existing flaw were conducted and the failure processes were recorded by using the high-speed camera. To quantitatively determine the crack initiation mechanism, a novel method was first proposed based on digital image correlation (DIC) analysis and then its validity was confirmed. By utilizing this method, three types of cracks with different initiation mechanisms were identified and the effect of flaw inclination angle on crack initiation mechanisms was discussed from the viewpoint of theoretical analysis. With the increase of inclination angles, wing cracks change from mixed mode I/II cracks to mode I cracks, while anti-wing cracks have no evident changes and are dominated by mode II cracks. Under compressive pressure, the upper and bottom surfaces of pre-existing flaw deform to each other and the distributions of full-field tangential stress around flaw are different, which might induce the variation of crack initiation mechanisms with regard to the inclination angle.

@article{
 title = {Simulation on heterogeneous rocks with a flaw using grain-based discrete-element method},
 type = {article},
 year = {2021},
 keywords = {Discrete-element modelling,Mineralogy,Rocks/rock mechanics},
 pages = {55-65},
 volume = {11},
 id = {0f85d67d-67f5-329e-bc51-471104a4a546},
 created = {2021-09-23T16:01:52.897Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2022-02-23T17:05:51.670Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Liu2021},
 private_publication = {false},
 abstract = {To take into consideration the effect of mineral microstructure on crack growth and mechanical properties of heterogeneous rocks containing a single pre-existing flaw under uniaxial compression, the discrete-element method in combination with the grain-based model was adopted in this study. The results indicate that the characteristic stresses – that is, crack initiation stress, crack damage stress and peak strength, generally increase with respect to the inclination angle. The normalised crack initiation stress increases with the increasing angle, while the normalised crack damage stress has no pronounced change. Additionally, the variation of inclination angles has little influence on the grain-scale crack growth. The initiation of intergranular cracks is prior to the intragranular cracks, and the proportion of intragranular cracks is slightly greater than intergranular cracks at the peak failure moment. The ultimate failure patterns obtained by numerical simulations agree well with the experimental results, revealing the cracks generated from the pre-existing flaw consist of intragranular and intergranular cracks at the grain scale.},
 bibtype = {article},
 author = {Liu, L. and Li, H. and Li, X. and Zhou, C. and Zhang, G.},
 doi = {10.1680/jgele.20.00083},
 journal = {Geotechnique Letters},
 number = {1}
}

To take into consideration the effect of mineral microstructure on crack growth and mechanical properties of heterogeneous rocks containing a single pre-existing flaw under uniaxial compression, the discrete-element method in combination with the grain-based model was adopted in this study. The results indicate that the characteristic stresses – that is, crack initiation stress, crack damage stress and peak strength, generally increase with respect to the inclination angle. The normalised crack initiation stress increases with the increasing angle, while the normalised crack damage stress has no pronounced change. Additionally, the variation of inclination angles has little influence on the grain-scale crack growth. The initiation of intergranular cracks is prior to the intragranular cracks, and the proportion of intragranular cracks is slightly greater than intergranular cracks at the peak failure moment. The ultimate failure patterns obtained by numerical simulations agree well with the experimental results, revealing the cracks generated from the pre-existing flaw consist of intragranular and intergranular cracks at the grain scale.

@inproceedings{
 title = {Mechanical characteristics and failure process of fractured rocks with a single pre-existing flaw: DEM simulation based on discrete fracture network},
 type = {inproceedings},
 year = {2021},
 pages = {452-458},
 volume = {1},
 publisher = {OnePetro},
 id = {2652b019-cb3e-3c7b-afbb-91d278a5e939},
 created = {2021-11-09T21:14:58.841Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2022-02-23T17:05:51.788Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Liu2021b},
 source_type = {CONF},
 private_publication = {false},
 abstract = {Discrete fracture network is a crucial factor that influences the failure of geomaterials and the construction of rock engineering, the initiation, propagation, and coalescence of cracks emanating from pre-existing flaws lead to material failure under the compressive loading. To investigate the mechanical characteristics and failure processes of fractured rocks containing a flaw, four models with different fracture numbers were established based on the discrete element method, two contact models were used to describe the mechanical behaviors of fractures and rock matrix, then the uniaxial compressive tests were mimicked in this study. The results indicate that the peak strength of models decreases generally with the increase of fracture number, which is due to the growth of microcracks generated in fractures. The percentage of cracks formed in fractures increases regarding the fracture number, while the proportion of cracks in the rock matrix decreases, revealing the reason why the peak strength presents a decreasing tendency. Furthermore, wing cracks, at the onset of axial loading, firstly initiated from flaw tips due to the stress concentration, and the increasing fracture number has no obvious impact on the initiation characteristics of cracks. As the axial stress increases, crack propagation and coalescence lead to the model failure. As the fracture number increases, the coalescence is mainly induced by the cracks formed in fractures, and the ultimate failure pattern becomes more complicated.},
 bibtype = {inproceedings},
 author = {Liu, Liwang and Li, Haibo and Wu, Di and Zhou, Jun and Fu, Shuaiyang and Li, Xiaofeng},
 booktitle = {55th U.S. Rock Mechanics / Geomechanics Symposium 2021}
}

Discrete fracture network is a crucial factor that influences the failure of geomaterials and the construction of rock engineering, the initiation, propagation, and coalescence of cracks emanating from pre-existing flaws lead to material failure under the compressive loading. To investigate the mechanical characteristics and failure processes of fractured rocks containing a flaw, four models with different fracture numbers were established based on the discrete element method, two contact models were used to describe the mechanical behaviors of fractures and rock matrix, then the uniaxial compressive tests were mimicked in this study. The results indicate that the peak strength of models decreases generally with the increase of fracture number, which is due to the growth of microcracks generated in fractures. The percentage of cracks formed in fractures increases regarding the fracture number, while the proportion of cracks in the rock matrix decreases, revealing the reason why the peak strength presents a decreasing tendency. Furthermore, wing cracks, at the onset of axial loading, firstly initiated from flaw tips due to the stress concentration, and the increasing fracture number has no obvious impact on the initiation characteristics of cracks. As the axial stress increases, crack propagation and coalescence lead to the model failure. As the fracture number increases, the coalescence is mainly induced by the cracks formed in fractures, and the ultimate failure pattern becomes more complicated.

@article{
 title = {Investigating the mechanism of rock fracturing induced by high-pressure gas blasting with a hybrid continuum-discontinuum method},
 type = {article},
 year = {2021},
 keywords = {Blast,Fragmentation,High-pressure gas blasting,Hybrid continuum-discontinuum method,Rock fracturing},
 pages = {104445},
 volume = {140},
 month = {12},
 id = {5204ac41-4fc2-3fe5-8649-ec57cd02c1cc},
 created = {2021-11-09T21:14:59.118Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2023-10-12T02:55:29.517Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Wang2021d},
 source_type = {JOUR},
 private_publication = {false},
 abstract = {To study the rock-breaking mechanism resulting from high-pressure gas blasting, a hybrid continuum-discontinuum method considering the actual breakage of rocks was presented in this study. The mechanical parameters were calibrated against the uniaxial compression test and Brazilian disc test, and the capabilities of simulating blast-induced fractures were verified by laboratory tests. After that, the differences in rock-breaking mechanism between explosive blasting and high-pressure gas blasting were compared from the perspectives of peak pressure and loading rate. The results indicated that the crack patterns, fracture mode and vibration attenuation induced by high-pressure gas blasting were significantly different from that of explosive blasting: (a) no crushing zone and fewer radial cracks were formed in high-pressure gas blasting and the spalling cracks were absent near the free face in high-pressure gas blasting; (b) the difference of rock fracture mode in high-pressure gas blasting and explosive blasting indicated that the tensile fracturing was the dominant fracture mode in high pressure gas blasting which is different from the catastrophic fragments due to compressive-sheared fracturing surrounding the borehole in explosive blasting; (c) the intensity and attenuation factors of peak particle velocity both increased with the increase of peak pressure or loading rate, which indicated that the peak particle velocity induced by explosive blasting results in more intense and faster attenuated vibration disasters than that of high-pressure gas blasting.},
 bibtype = {article},
 author = {Wang, Ben and Li, Haibo and Shao, Zhushan and Chen, Shihai and Li, Xiaofeng},
 doi = {10.1016/j.compgeo.2021.104445},
 journal = {Computers and Geotechnics},
 number = {1}
}

To study the rock-breaking mechanism resulting from high-pressure gas blasting, a hybrid continuum-discontinuum method considering the actual breakage of rocks was presented in this study. The mechanical parameters were calibrated against the uniaxial compression test and Brazilian disc test, and the capabilities of simulating blast-induced fractures were verified by laboratory tests. After that, the differences in rock-breaking mechanism between explosive blasting and high-pressure gas blasting were compared from the perspectives of peak pressure and loading rate. The results indicated that the crack patterns, fracture mode and vibration attenuation induced by high-pressure gas blasting were significantly different from that of explosive blasting: (a) no crushing zone and fewer radial cracks were formed in high-pressure gas blasting and the spalling cracks were absent near the free face in high-pressure gas blasting; (b) the difference of rock fracture mode in high-pressure gas blasting and explosive blasting indicated that the tensile fracturing was the dominant fracture mode in high pressure gas blasting which is different from the catastrophic fragments due to compressive-sheared fracturing surrounding the borehole in explosive blasting; (c) the intensity and attenuation factors of peak particle velocity both increased with the increase of peak pressure or loading rate, which indicated that the peak particle velocity induced by explosive blasting results in more intense and faster attenuated vibration disasters than that of high-pressure gas blasting.

@article{
 title = {Large-scale asymmetric pulverisation of fault zone: Insights from rock axial strain in static and dynamic loading conditions},
 type = {article},
 year = {2021},
 keywords = {Asymmetric pulverisation,Axial strain,Cyclic dynamic load,Fault zone,Rock stiffness},
 pages = {104557},
 volume = {137},
 month = {1},
 publisher = {Elsevier Ltd},
 day = {1},
 id = {a3a680ca-2f01-3e3f-988a-a0b1396dd310},
 created = {2022-02-23T16:53:45.635Z},
 accessed = {2021-01-21},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2025-03-13T16:56:55.919Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Ju2021b},
 private_publication = {false},
 abstract = {The open question of asymmetric large-scale pulverisation of fault zone was experimentally investigated in this paper. It is found that the transition of rock fracture from local splitting to pervasive pulverisation is controlled by strain both in quasi-static and dynamic conditions. This can explain the asymmetric damage in the fault zone as the strain threshold to pulverisation for stiffer rock is lower. In terms of the cyclic dynamic loadings, four types of fracture patterns (lateral tension, axial split, spatial fragmentation, and pervasive pulverisation) were developed with the increase of strain. Subject to the long-term quasi-static and dynamic load, the cumulative damage to the fault zone broadens the scale of pulverisation. In light of the linear correlation of energy absorption to strain, the damage relationships between strain and loading cycles were established and found to offer a good prediction of experimental data.},
 bibtype = {article},
 author = {Ju, Minghe and Li, Xiaofeng and Li, Jianchun},
 doi = {10.1016/j.ijrmms.2020.104557},
 journal = {International Journal of Rock Mechanics and Mining Sciences}
}

The open question of asymmetric large-scale pulverisation of fault zone was experimentally investigated in this paper. It is found that the transition of rock fracture from local splitting to pervasive pulverisation is controlled by strain both in quasi-static and dynamic conditions. This can explain the asymmetric damage in the fault zone as the strain threshold to pulverisation for stiffer rock is lower. In terms of the cyclic dynamic loadings, four types of fracture patterns (lateral tension, axial split, spatial fragmentation, and pervasive pulverisation) were developed with the increase of strain. Subject to the long-term quasi-static and dynamic load, the cumulative damage to the fault zone broadens the scale of pulverisation. In light of the linear correlation of energy absorption to strain, the damage relationships between strain and loading cycles were established and found to offer a good prediction of experimental data.

@article{
 title = {Transgranular fracturing of crystalline rocks and its influence on rock strengths: Insights from a grain-scale continuum–discontinuum approach},
 type = {article},
 year = {2021},
 keywords = {Heterogeneity,Hybrid continuum–discontinuum,Inter/transgranular fracturing,Multiscale grain-based model,Rocks},
 pages = {113462},
 volume = {373},
 month = {1},
 id = {5b4d6cc8-08c1-353c-a0c7-3a0fcac73d80},
 created = {2022-02-23T16:53:45.636Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2023-10-12T02:55:29.168Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Li2021g},
 private_publication = {false},
 abstract = {The aim of this study is to understand the effects of micro-heterogeneity, such as grain size, morphology and mineralogy, on the initiation, propagation and coalescence of microcracks in heterogeneous materials. A multiscale grain-breakable continuum–discontinuum model incorporating realistic micro-heterogeneity reproduction method is proposed to investigate the fracturing behaviours and confinement mechanism of rocks. Crack initiation and damage stresses are intrinsic properties of rocks determined by grain-scale heterogeneity. Intergranular tensile cracks are primarily initiated as a result of local stress heterogeneity along grain boundaries. The subsequent generation of transgranular shear cracks implies a rapid proliferation of grain-crossing fractures, leads to large-scale crack interaction and coalescence. The effect of confinement inhibits crack extension and increases the appearance of shear-induced grain pulverizations. Furthermore, the effects of grain size, grain morphology and mineralogy on macro mechanical properties, including crack initiation stress, crack damage stress, uniaxial compression strength and elastic modulus, are discussed. The simulated results indicate that the larger grain size contributes to stronger local stress heterogeneity, which results in a lower failure strength of rocks. The crack initiation stress is determined by local heterogeneity and is less affected by the change in average grain size. Grain morphology plays an important role in grain interlocking while a reduction in grain size variance leads to a more homogeneous stress field. The mineralogy is evaluated with the aid of a quartz-mica-feldspar diagram, and the quantitative relationships between mineralogy and the macro-scale mechanical properties of rocks are discussed.},
 bibtype = {article},
 author = {Li, X. F. and Li, H. B. and Zhao, J.},
 doi = {10.1016/j.cma.2020.113462},
 journal = {Computer Methods in Applied Mechanics and Engineering}
}

The aim of this study is to understand the effects of micro-heterogeneity, such as grain size, morphology and mineralogy, on the initiation, propagation and coalescence of microcracks in heterogeneous materials. A multiscale grain-breakable continuum–discontinuum model incorporating realistic micro-heterogeneity reproduction method is proposed to investigate the fracturing behaviours and confinement mechanism of rocks. Crack initiation and damage stresses are intrinsic properties of rocks determined by grain-scale heterogeneity. Intergranular tensile cracks are primarily initiated as a result of local stress heterogeneity along grain boundaries. The subsequent generation of transgranular shear cracks implies a rapid proliferation of grain-crossing fractures, leads to large-scale crack interaction and coalescence. The effect of confinement inhibits crack extension and increases the appearance of shear-induced grain pulverizations. Furthermore, the effects of grain size, grain morphology and mineralogy on macro mechanical properties, including crack initiation stress, crack damage stress, uniaxial compression strength and elastic modulus, are discussed. The simulated results indicate that the larger grain size contributes to stronger local stress heterogeneity, which results in a lower failure strength of rocks. The crack initiation stress is determined by local heterogeneity and is less affected by the change in average grain size. Grain morphology plays an important role in grain interlocking while a reduction in grain size variance leads to a more homogeneous stress field. The mineralogy is evaluated with the aid of a quartz-mica-feldspar diagram, and the quantitative relationships between mineralogy and the macro-scale mechanical properties of rocks are discussed.

@article{
 title = {Rate dependency mechanism of crystalline rocks induced by impacts: Insights from grain-scale fracturing and micro heterogeneity},
 type = {article},
 year = {2021},
 keywords = {Grain-based model,Impact,Multiscale fracturing,Rock heterogeneity,Strain rate dependency},
 pages = {103855},
 volume = {155},
 month = {9},
 id = {0f81226e-f431-3b89-b647-bacd64139a4c},
 created = {2022-02-23T16:53:45.638Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2023-10-12T02:55:29.095Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Li2021h},
 private_publication = {false},
 abstract = {Rocks in nature contain a large number of defects and exhibit strong heterogeneity on grain scale. In this study, a novel three-dimensional multiscale method is proposed to investigate the dynamic behaviors and microfracturing in granitic rocks. In this numerical method, the heterogeneity in mineral components is reproduced by a series of a space filling Voronoi tessellations and particle filling in subgrains as computational nodal points to allow for transgranular fracturing. The rupture strength, temporal deformation fields, and failure patterns are compared with the experimental results to verify the reasonability and accuracy of the proposed method. Then, the underlying mechanism of grain-scale fracturing leading to fractal fracture surfaces, pervasively grain pulverization and deflection/penetration cracking model are discussed. It's shown that the fracture surface roughness is fractal dominated by two competitive mechanisms. The crack initiation time of intergranular tensile crack, transgranular tensile crack and shear cracks is gradually increased. The ratio of the number of tensile cracks exceeds 90% and that value of intergranular crack decreases from 56% to 33% as the strain rate increases. The appearance of multicracks activation and the transition from intergranular fracturing to transgranular fracturing is the underlying mechanism of rate dependency for granitic rocks.},
 bibtype = {article},
 author = {Li, X. F. and Li, H. B. and Zhang, G. K. and Ju, M. H. and Zhao, Jian},
 doi = {10.1016/j.ijimpeng.2021.103855},
 journal = {International Journal of Impact Engineering},
 number = {February}
}

Rocks in nature contain a large number of defects and exhibit strong heterogeneity on grain scale. In this study, a novel three-dimensional multiscale method is proposed to investigate the dynamic behaviors and microfracturing in granitic rocks. In this numerical method, the heterogeneity in mineral components is reproduced by a series of a space filling Voronoi tessellations and particle filling in subgrains as computational nodal points to allow for transgranular fracturing. The rupture strength, temporal deformation fields, and failure patterns are compared with the experimental results to verify the reasonability and accuracy of the proposed method. Then, the underlying mechanism of grain-scale fracturing leading to fractal fracture surfaces, pervasively grain pulverization and deflection/penetration cracking model are discussed. It's shown that the fracture surface roughness is fractal dominated by two competitive mechanisms. The crack initiation time of intergranular tensile crack, transgranular tensile crack and shear cracks is gradually increased. The ratio of the number of tensile cracks exceeds 90% and that value of intergranular crack decreases from 56% to 33% as the strain rate increases. The appearance of multicracks activation and the transition from intergranular fracturing to transgranular fracturing is the underlying mechanism of rate dependency for granitic rocks.

@article{
 title = {强冲击荷载下岩石材料断裂及破碎机制研究},
 type = {article},
 year = {2021},
 pages = {432},
 volume = {40},
 id = {910806b1-c446-3a39-ab73-fb98f9fbc2d7},
 created = {2022-02-23T16:57:37.196Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2023-10-12T02:55:29.455Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {2021b},
 source_type = {JOUR},
 private_publication = {false},
 bibtype = {article},
 author = {李晓锋, undefined},
 journal = {岩石力学与工程学报},
 number = {2}
}

@article{
 title = {Full-field strain evolution and characteristic stress levels of rocks containing a single pre-existing flaw under uniaxial compression},
 type = {article},
 year = {2020},
 keywords = {Characteristic stress levels,Digital image correlation method,Discrete element method,Full-field strain evolution,Pre-existing flaw},
 pages = {3145-3161},
 volume = {79},
 publisher = {Bulletin of Engineering Geology and the Environment},
 id = {2df2dc16-ae36-3232-877f-e4bbc79f252b},
 created = {2021-02-03T06:21:29.540Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2021-11-14T01:17:50.143Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Liu2020j},
 folder_uuids = {39d0a507-1c2f-432d-869a-ab44a4ea75f9},
 private_publication = {false},
 abstract = {In this study, full-field strain evolution and characteristic stress levels of marble samples containing a single pre-existing flaw were comprehensively studied. The full-field strain was performed by digital image correlation (DIC) method, and the variations of characteristic stress levels with respect to inclination angle were discussed. To compare the experimental results, discrete element method was adopted, and the full-field stress evolution was reproduced to reappraise the localization zones. The results indicate that the presence of pre-existing flaws induces strain localization and degradation of mechanical properties for pre-cracked samples. When the strain localization firstly appeared surrounding pre-existing flaws, the axial stress levels at this moment increase with regard to inclination angle, leading to the increase of peak strength, crack initiation stress, crack damage stress, and normalized crack initiation stress. The normalized crack damage stress obtained by experiments shows flaw independency, and the results were verified by simulation results. Based on the full-field stress evolution, the tensile stress in x direction concentrates around pre-existing flaw and its location moves towards flaw tips with the increase of inclination angle. The compressive stress in y direction around pre-existing flaw is lower than other zones, revealing the upper and bottom surfaces of pre-existing flaw deform to each other. When the numerical models are subjected to same axial loading, the full-field stress around pre-existing flaw decrease as the inclination angle increases, which confirmed the results of full-field strain evolution and elucidated the pre-existing flaw with large inclination angle has less effect on degrading the mechanical properties.},
 bibtype = {article},
 author = {Liu, Liwang and Li, Haibo and Li, Xiaofeng and Wu, Renjie},
 doi = {10.1007/s10064-020-01764-4},
 journal = {Bulletin of Engineering Geology and the Environment},
 number = {6}
}

In this study, full-field strain evolution and characteristic stress levels of marble samples containing a single pre-existing flaw were comprehensively studied. The full-field strain was performed by digital image correlation (DIC) method, and the variations of characteristic stress levels with respect to inclination angle were discussed. To compare the experimental results, discrete element method was adopted, and the full-field stress evolution was reproduced to reappraise the localization zones. The results indicate that the presence of pre-existing flaws induces strain localization and degradation of mechanical properties for pre-cracked samples. When the strain localization firstly appeared surrounding pre-existing flaws, the axial stress levels at this moment increase with regard to inclination angle, leading to the increase of peak strength, crack initiation stress, crack damage stress, and normalized crack initiation stress. The normalized crack damage stress obtained by experiments shows flaw independency, and the results were verified by simulation results. Based on the full-field stress evolution, the tensile stress in x direction concentrates around pre-existing flaw and its location moves towards flaw tips with the increase of inclination angle. The compressive stress in y direction around pre-existing flaw is lower than other zones, revealing the upper and bottom surfaces of pre-existing flaw deform to each other. When the numerical models are subjected to same axial loading, the full-field stress around pre-existing flaw decrease as the inclination angle increases, which confirmed the results of full-field strain evolution and elucidated the pre-existing flaw with large inclination angle has less effect on degrading the mechanical properties.

@article{
 title = {Experimental Study and Numerical Simulation of the Dynamic Behavior of Transversely Isotropic Phyllite},
 type = {article},
 year = {2020},
 pages = {04020105},
 volume = {20},
 id = {1b4e44df-1774-3ee2-b374-2b922cff5b5b},
 created = {2021-07-02T10:59:15.284Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2021-11-14T01:17:49.569Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Wu2020a},
 private_publication = {false},
 abstract = {Understanding the dynamic mechanical behavior of transversely isotropic rocks is essential in various fields of rock engineering, such as tunnel digging, blasting, and underground excavation. The bedding structure and strain rate determine the failure features of transversely isotropic rocks. Dynamic compression tests of transversely isotropic phyllites with different bedding angles were carried out using the split Hopkinson pressure bar (SHPB) approach to study the dynamic mechanical properties of transversely isotropic rocks. The resulting failure modes were characterized as two types (class I and class II) to describe the deformation behavior and fracture patterns under different strain rates. Both the strain rate and bedding angle influence the dynamic compressive strength. The dynamic compressive strength changes in a U-shaped trend as the bedding angle increases under similar strain rates. This trend becomes more pronounced as the strain rate increases. The failure patterns of the specimens tested under different strain rates are diverse. To gain a better understanding of the dynamic compressive behavior of phyllite, the discrete element method (DEM) was utilized to reveal the microfracture mechanism and failure process under extreme loads with the help of SHPB testing. The validity of the numerical simulation was verified by comparing the numerical results with the laboratory results. The thresholds dividing class I and class II failure for different bedding angles were investigated by applying different impact velocities. A scaling law was proposed to describe the increase in the dynamic strength of transversely isotropic phyllites. In addition, the microcrack propagation and microcrack type were analyzed to explore the influence of the bedding structures on the failure pattern and compressive strength. Different failure patterns form from different microcrack propagation processes, and the resistance of microcrack generation determines the strength of phyllites with different bedding angles.},
 bibtype = {article},
 author = {Wu, Renjie and Li, Haibo and Li, Xiaofeng and Xia, Xiang and Liu, Liwang},
 doi = {10.1061/(asce)gm.1943-5622.0001737},
 journal = {International Journal of Geomechanics},
 number = {8}
}

Understanding the dynamic mechanical behavior of transversely isotropic rocks is essential in various fields of rock engineering, such as tunnel digging, blasting, and underground excavation. The bedding structure and strain rate determine the failure features of transversely isotropic rocks. Dynamic compression tests of transversely isotropic phyllites with different bedding angles were carried out using the split Hopkinson pressure bar (SHPB) approach to study the dynamic mechanical properties of transversely isotropic rocks. The resulting failure modes were characterized as two types (class I and class II) to describe the deformation behavior and fracture patterns under different strain rates. Both the strain rate and bedding angle influence the dynamic compressive strength. The dynamic compressive strength changes in a U-shaped trend as the bedding angle increases under similar strain rates. This trend becomes more pronounced as the strain rate increases. The failure patterns of the specimens tested under different strain rates are diverse. To gain a better understanding of the dynamic compressive behavior of phyllite, the discrete element method (DEM) was utilized to reveal the microfracture mechanism and failure process under extreme loads with the help of SHPB testing. The validity of the numerical simulation was verified by comparing the numerical results with the laboratory results. The thresholds dividing class I and class II failure for different bedding angles were investigated by applying different impact velocities. A scaling law was proposed to describe the increase in the dynamic strength of transversely isotropic phyllites. In addition, the microcrack propagation and microcrack type were analyzed to explore the influence of the bedding structures on the failure pattern and compressive strength. Different failure patterns form from different microcrack propagation processes, and the resistance of microcrack generation determines the strength of phyllites with different bedding angles.

@article{
 title = {Broken energy dissipation and fragmentation characteristics of layered rock under impact loading},
 type = {article},
 year = {2020},
 keywords = {Broken energy dissipation,Dynamic compression,Fragmentation distribution,Layered rock},
 pages = {1053-1060},
 volume = {45},
 id = {de576b46-c939-36f4-83e2-2aa03f4c4831},
 created = {2021-11-09T21:14:59.116Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2021-11-14T01:17:49.664Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Wu2019g},
 source_type = {JOUR},
 private_publication = {false},
 abstract = {By using split Hopkinson pressure bar(SHPB) test apparatus, the dynamic compression tests of layered rocks with different bedding dips of 0°, 22.5°, 45°, 67.5° and 90° under different impact velocities were carried out in this study. The fragmentation distribution characteristics of layered rocks were compared and analyzed according to sieving the crushed sample debris. The reflection energy, transmission energy, dissipated energy density and fragmentation under different incident energies were discussed. Results show that for the sample with same bedding dip angle, the average particle size gradually decreases as the impact velocity increases. At the same impact velocity, the fracture degree of the specimen with a dip angle of 67.5° is the largest, and the 0° sample is the smallest. Fractal dimension can quantitatively characterize the fragmentation distribution characteristics. The fractal dimension is larger when the fragmentation is smaller. At the same incident energy, the dissipation energy density of the 90° sample is the largest, while the dissipation energy density of specimens with 0° or 22.5° dip angle is smaller, which reveal that a high dip angle has a higher energy utilization rate, and 0° or 22.5° is lower. At the same incident energy, the 90° samples have higher reflective energy, and the layered rocks with 0° and 22.5° dip angles have higher transmission energy, which indicates that the reactive power dissipates mostly in the form of reflection waveform at high dip angle and mostly in the form of transmission waveform at low dip angle. The reflection energy, transmission energy and dissipation energy density increase with the increase of incident energy. The fractal dimension increases with the increase of dissipation energy density. With the increase of energy consumption at high dip angle, the sample breaks more severely. With the increase of dissipated energy density at low dip angle, the trend of sample fragmentation changes little, and the energy required to produce new cracks and fracture surfaces is high. In engineering practices, if the dynamic loading angle of 45.0°-67.5° is selected, not only the strength of rock is low, and the rock sample breaks more severely, but also the energy utilization rate is high.},
 bibtype = {article},
 author = {Wu, Renjie and Li, Haibo and Li, Xiaofeng and Yu, Chong and Xia, Xiang and Liu, Liwang},
 doi = {10.13225/j.cnki.jccs.2019.0266},
 journal = {Meitan Xuebao/Journal of the China Coal Society},
 number = {3}
}

By using split Hopkinson pressure bar(SHPB) test apparatus, the dynamic compression tests of layered rocks with different bedding dips of 0°, 22.5°, 45°, 67.5° and 90° under different impact velocities were carried out in this study. The fragmentation distribution characteristics of layered rocks were compared and analyzed according to sieving the crushed sample debris. The reflection energy, transmission energy, dissipated energy density and fragmentation under different incident energies were discussed. Results show that for the sample with same bedding dip angle, the average particle size gradually decreases as the impact velocity increases. At the same impact velocity, the fracture degree of the specimen with a dip angle of 67.5° is the largest, and the 0° sample is the smallest. Fractal dimension can quantitatively characterize the fragmentation distribution characteristics. The fractal dimension is larger when the fragmentation is smaller. At the same incident energy, the dissipation energy density of the 90° sample is the largest, while the dissipation energy density of specimens with 0° or 22.5° dip angle is smaller, which reveal that a high dip angle has a higher energy utilization rate, and 0° or 22.5° is lower. At the same incident energy, the 90° samples have higher reflective energy, and the layered rocks with 0° and 22.5° dip angles have higher transmission energy, which indicates that the reactive power dissipates mostly in the form of reflection waveform at high dip angle and mostly in the form of transmission waveform at low dip angle. The reflection energy, transmission energy and dissipation energy density increase with the increase of incident energy. The fractal dimension increases with the increase of dissipation energy density. With the increase of energy consumption at high dip angle, the sample breaks more severely. With the increase of dissipated energy density at low dip angle, the trend of sample fragmentation changes little, and the energy required to produce new cracks and fracture surfaces is high. In engineering practices, if the dynamic loading angle of 45.0°-67.5° is selected, not only the strength of rock is low, and the rock sample breaks more severely, but also the energy utilization rate is high.

@article{
 title = {Crack initiation of granite under uniaxial compression tests: A comparison study},
 type = {article},
 year = {2020},
 keywords = {Acoustic emission (AE),Crack initiation (CI) stress,Granite,Ultrasonic transmission,Wave velocity},
 pages = {656-666},
 volume = {12},
 id = {54b0b9de-d6d2-37ff-a67f-61ef37ec5702},
 created = {2022-02-23T16:53:45.335Z},
 file_attached = {true},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2022-02-23T17:05:51.892Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Zhang2020e},
 folder_uuids = {6cf311a7-6997-405c-97e7-91c89f2f9e1b},
 private_publication = {false},
 abstract = {In this study, a combination of acoustic emission (AE) method (AEM) and wave transmission method (WTM) is used to investigate the behaviors of AE and ultrasonic properties corresponding to initial fracturing in granitic rocks. The relationships of AE characteristics, frequency spectra, and spatial locations with crack initiation (CI) are studied. The anisotropic ultrasonic characteristics, velocity distributions in different ray paths, wave amplitudes, and spectral characters of transmitted waves are investigated. To identify CI stress, damage initiations characterized by strain-based method (SBM), AEM and WTM are compared. For granite samples, it shows that the ratio of CI stress to peak strength estimated by SBM ranges from 0.4 to 0.55, and 0.49–0.6 by WTM, which are higher than that of AEM (0.38–0.46). The CI stress identified by AEM indicates the onset of microcracking, and the combination of AEM and WTM provides an insight into the detection of rock damage initiation and anisotropy.},
 bibtype = {article},
 author = {Zhang, G. K. and Li, H. B. and Wang, M. Y. and Li, X. F.},
 doi = {10.1016/j.jrmge.2019.07.014},
 journal = {Journal of Rock Mechanics and Geotechnical Engineering},
 number = {3}
}

In this study, a combination of acoustic emission (AE) method (AEM) and wave transmission method (WTM) is used to investigate the behaviors of AE and ultrasonic properties corresponding to initial fracturing in granitic rocks. The relationships of AE characteristics, frequency spectra, and spatial locations with crack initiation (CI) are studied. The anisotropic ultrasonic characteristics, velocity distributions in different ray paths, wave amplitudes, and spectral characters of transmitted waves are investigated. To identify CI stress, damage initiations characterized by strain-based method (SBM), AEM and WTM are compared. For granite samples, it shows that the ratio of CI stress to peak strength estimated by SBM ranges from 0.4 to 0.55, and 0.49–0.6 by WTM, which are higher than that of AEM (0.38–0.46). The CI stress identified by AEM indicates the onset of microcracking, and the combination of AEM and WTM provides an insight into the detection of rock damage initiation and anisotropy.

@article{
 title = {Investigating the crack initiation and propagation mechanism in brittle rocks using grain-based finite-discrete element method},
 type = {article},
 year = {2020},
 keywords = {Crack stress,Finite-discrete element model,Micro fracturing,Realistic granular model,Rock heterogeneity},
 volume = {127},
 id = {871bafe8-0173-322e-b598-81a72e500688},
 created = {2022-02-23T16:53:45.636Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2023-10-12T02:55:28.910Z},
 read = {true},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Li2020i},
 private_publication = {false},
 abstract = {Fracturing process and possible factors influencing crack initiation, propagation and coalescence of granitic rocks are investigated using a grain-based finite-discrete element method (GB-FDEM). In contrast to conventional methods, the GB-FDEM used herein consists of dual-scale contact models ensuring grain breakage, and pre-processing scheme for reproducing the realistic micro heterogeneity of rocks. A standardised calibration procedure is proposed after an analysis of uncertain parameters. An optimized model is built according to calibration results of benchmark experiments including uniaxial compression test, confined compression test and Brazilian disc test in laboratory. The compression testing under different end friction, slenderness, loading rate and confining stress are systematically performed to investigate the external influences on rock fracturing. Boundary constraint is revealed in association with the macro failure pattern, in which the shearing slide leads to slight extension on ends and causes limited influence on the stress distribution in the far field. Effects on crack stresses are consistent with that of uniaxial compressive strength when the end friction takes effect. Slenderness affects the stress distribution and in turn changes the fracture pattern of rocks. Slight influence on the stress level of crack initiation and crack damage can be caused by the change of height-to-width ratio. Loading rate dramatically increase the rock strength based on two underlying mechanisms that the increase in overall number of micro cracks and the transition from intergranular fracturing to transgranular fracturing. These effects on crack initiation and crack damage stresses are inconsistent because the responses of normalized crack initiation and crack damage stresses subject to strain rate have inverse responses. The proportion of different micro cracks is shown to characterize the unchanged micro fracturing when the confining stress is increased. The enhancement of crack initiation and the change of the pattern of crack coalescence are attributed as the mechanism of confinement effect.},
 bibtype = {article},
 author = {Li, X. F. and Li, H. B. and Liu, L. W. and Liu, Y. Q. and Ju, M. H. and Zhao, J.},
 doi = {10.1016/j.ijrmms.2020.104219},
 journal = {International Journal of Rock Mechanics and Mining Sciences},
 number = {October 2018}
}

Fracturing process and possible factors influencing crack initiation, propagation and coalescence of granitic rocks are investigated using a grain-based finite-discrete element method (GB-FDEM). In contrast to conventional methods, the GB-FDEM used herein consists of dual-scale contact models ensuring grain breakage, and pre-processing scheme for reproducing the realistic micro heterogeneity of rocks. A standardised calibration procedure is proposed after an analysis of uncertain parameters. An optimized model is built according to calibration results of benchmark experiments including uniaxial compression test, confined compression test and Brazilian disc test in laboratory. The compression testing under different end friction, slenderness, loading rate and confining stress are systematically performed to investigate the external influences on rock fracturing. Boundary constraint is revealed in association with the macro failure pattern, in which the shearing slide leads to slight extension on ends and causes limited influence on the stress distribution in the far field. Effects on crack stresses are consistent with that of uniaxial compressive strength when the end friction takes effect. Slenderness affects the stress distribution and in turn changes the fracture pattern of rocks. Slight influence on the stress level of crack initiation and crack damage can be caused by the change of height-to-width ratio. Loading rate dramatically increase the rock strength based on two underlying mechanisms that the increase in overall number of micro cracks and the transition from intergranular fracturing to transgranular fracturing. These effects on crack initiation and crack damage stresses are inconsistent because the responses of normalized crack initiation and crack damage stresses subject to strain rate have inverse responses. The proportion of different micro cracks is shown to characterize the unchanged micro fracturing when the confining stress is increased. The enhancement of crack initiation and the change of the pattern of crack coalescence are attributed as the mechanism of confinement effect.

@article{
 title = {Crack-induced acoustic emission and anisotropy variation of brittle rocks containing natural fractures},
 type = {article},
 year = {2019},
 keywords = {AE hypocenters,Ultrasonic velocity,acoustic emission,anisotropy parameter,crack initiation,natural fracture},
 pages = {599-610},
 volume = {16},
 id = {03cf2a35-6646-3e67-9163-1dd10c6ce1a2},
 created = {2019-07-17T23:59:00.000Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2021-11-14T01:17:49.586Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Zhang2019k},
 private_publication = {false},
 abstract = {The acoustic emission (AE), ultrasonic velocity and stress-strain behaviors of brittle rocks containing natural fractures were simultaneously measured under uniaxial compression. An optimized sparse network of transducers was used to monitor the crack-induced AE activities and changes of velocities in different directions. The variation of rock anisotropy was co-characterized by wave velocity and localization of AE hypocenters. The microscale behaviors of rock failure were investigated by the analysis of AE waveforms and multiple characteristic parameters. A flurry of AEs behaving at low frequency and low amplitude appear even under a low stress level for fractured rocks. With an increase of stress, the initiation of cracks first occurs along the natural fracture accompany with increased dominant frequency, then decreases rapidly after the coalescence of cracks. The natural fracture is the main source of rock anisotropy, which decreases first as the pressure-induced closure of fracture, then increases with the opening of cracks along the fracture. For rocks with a higher inclined fracture, the anisotropy parameter is more sensitive to the initiation, propagation and coalescence of cracks. Unexpectedly, the increase of AEs occurs much earlier than the inflection of velocity, and AE hypocenters based on the time-variable velocity depicts the localization and propagation of cracks well. AE energy increases precipitously after 98% peak strength, accompanied with the sharp increase in the ratio of low-frequency AEs, which is a perfect precursor of potentially unstable nucleation.},
 bibtype = {article},
 author = {Zhang, Guokai and Li, Haibo and Wang, Mingyang and Li, Xiaofeng and Wang, Zhen and Deng, Shuxin},
 doi = {10.1093/jge/gxz031},
 journal = {Journal of Geophysics and Engineering},
 number = {3}
}

The acoustic emission (AE), ultrasonic velocity and stress-strain behaviors of brittle rocks containing natural fractures were simultaneously measured under uniaxial compression. An optimized sparse network of transducers was used to monitor the crack-induced AE activities and changes of velocities in different directions. The variation of rock anisotropy was co-characterized by wave velocity and localization of AE hypocenters. The microscale behaviors of rock failure were investigated by the analysis of AE waveforms and multiple characteristic parameters. A flurry of AEs behaving at low frequency and low amplitude appear even under a low stress level for fractured rocks. With an increase of stress, the initiation of cracks first occurs along the natural fracture accompany with increased dominant frequency, then decreases rapidly after the coalescence of cracks. The natural fracture is the main source of rock anisotropy, which decreases first as the pressure-induced closure of fracture, then increases with the opening of cracks along the fracture. For rocks with a higher inclined fracture, the anisotropy parameter is more sensitive to the initiation, propagation and coalescence of cracks. Unexpectedly, the increase of AEs occurs much earlier than the inflection of velocity, and AE hypocenters based on the time-variable velocity depicts the localization and propagation of cracks well. AE energy increases precipitously after 98% peak strength, accompanied with the sharp increase in the ratio of low-frequency AEs, which is a perfect precursor of potentially unstable nucleation.

@article{
 title = {The role of transgranular capability in grain-based modelling of crystalline rocks},
 type = {article},
 year = {2019},
 keywords = {Discrete element method (DEM) simulation,Grain crushing,Grain-based model,Heterogeneity,Intergranular and transgranular cracks},
 pages = {161-183},
 volume = {110},
 id = {ff7dec43-d6c4-31f0-a00b-1d7b73d68d89},
 created = {2022-02-23T16:53:45.333Z},
 file_attached = {true},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2022-02-23T17:05:51.872Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Li2019n},
 folder_uuids = {89c737c3-3080-497a-9e42-aeafdad30ca7},
 private_publication = {false},
 abstract = {Considering that many numerical methods have been developed to study the mechanical properties of rocks based on micro heterogeneities such as mineral size, morphology, composition and boundary defects, an overview of grain-based modelling is presented in this study to compare the advantages and limitations of different grain-mimicking methods. Intergranular and transgranular fracturing models and difficulties in parameter calibrations are discussed. Four typical grain models, UDEC-GBM, GB-FDEM, cluster and clump, are used to represent the two main families: block-based grains and particle-based grains with and without considering grain crushing. Subsequently, how grain crushing affects crack stresses, Hoek-Brown strength parameters m i , localized shearing and cracking transformation is simulated by these grain models. The simulated results indicate that the approaches capable of grain breakage lead to more consistent results in comparison with laboratory tests, for example, evident dilatancy in uniaxial compressive loading, high strength ratios, nonlinear failure strength envelopes and shear bands under high confinement. The role of transgranular capability is significantly important in the simulation of rock deformation using grain models.},
 bibtype = {article},
 author = {Li, X. F. and Li, H. B. and Zhao, J.},
 doi = {10.1016/j.compgeo.2019.02.018},
 journal = {Computers and Geotechnics},
 number = {November 2018}
}

Considering that many numerical methods have been developed to study the mechanical properties of rocks based on micro heterogeneities such as mineral size, morphology, composition and boundary defects, an overview of grain-based modelling is presented in this study to compare the advantages and limitations of different grain-mimicking methods. Intergranular and transgranular fracturing models and difficulties in parameter calibrations are discussed. Four typical grain models, UDEC-GBM, GB-FDEM, cluster and clump, are used to represent the two main families: block-based grains and particle-based grains with and without considering grain crushing. Subsequently, how grain crushing affects crack stresses, Hoek-Brown strength parameters m i , localized shearing and cracking transformation is simulated by these grain models. The simulated results indicate that the approaches capable of grain breakage lead to more consistent results in comparison with laboratory tests, for example, evident dilatancy in uniaxial compressive loading, high strength ratios, nonlinear failure strength envelopes and shear bands under high confinement. The role of transgranular capability is significantly important in the simulation of rock deformation using grain models.

@article{
 title = {Fracture surface morphology of brittle geomaterials influenced by loading rate and grain size},
 type = {article},
 year = {2019},
 keywords = {Crack deflection,Crack penetration,Dynamic loading,Grain size,Surface roughness},
 volume = {133},
 id = {a39caf9c-33a7-39eb-a237-e42b11732675},
 created = {2022-02-23T16:55:58.816Z},
 file_attached = {true},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2022-02-23T16:56:25.120Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Ju2019g},
 folder_uuids = {ae2757ab-34eb-461b-b313-4d85729d6f10},
 private_publication = {false},
 abstract = {The fracture surface roughness of grain-based geomaterials is one of the significant factors reflecting the changes in certain physical and mechanical properties. In this paper, the transition of fracture surface roughness of brittle geomaterials with loading rate was investigated theoretically and experimentally. The notched semi-circular bending (NSCB) method was used to clarify the morphology transition mechanism integrating both the macro and micro-fracturing aspects of grain-based structures. Two measurement techniques, high-speed digital image correlation and a crack propagation gauge, were applied to acquire real-time crack locations and crack propagating velocities of NSCB samples under various dynamic loads. Macroscopic failure data were verified via our modified rate-dependent theoretical model for the prediction of crack deflection and penetration. Then the typical parameter, joint roughness coefficient (JRC), was used to characterise the micro-features of each fracture surface at different loading rates. This parameter is quantified in terms of the fractal dimension through our image processing method. In light of the comparisons of three scenarios under different degrees of dynamic loading, the JRC values linearly decrease with loading rate, which is attributed to the predominant failure pattern of microscopic grains changing from deflection to penetration. In addition, micro-grains in larger size on fracture surface roughness are more sensitive to the increase of loading rate, e.g. in rock, resulting in a greater decrease of fracture surface roughness with respect to that in cement with small micro-grains. However, if the crack propagation velocity exceeds the critical value that contributing to the micro-cracks branching, the declined fracture surface roughness will increase monotonically with the loading rate. The results help to predict the failure pattern of two-phase structures in both quasi-static and dynamic conditions as well allowing quantitative analysis of fracture surface morphology under dynamic load.},
 bibtype = {article},
 author = {Ju, Minghe and Li, Jianchun and Li, Xiaofeng and Zhao, Jian},
 doi = {10.1016/j.ijimpeng.2019.103363},
 journal = {International Journal of Impact Engineering},
 number = {May}
}

The fracture surface roughness of grain-based geomaterials is one of the significant factors reflecting the changes in certain physical and mechanical properties. In this paper, the transition of fracture surface roughness of brittle geomaterials with loading rate was investigated theoretically and experimentally. The notched semi-circular bending (NSCB) method was used to clarify the morphology transition mechanism integrating both the macro and micro-fracturing aspects of grain-based structures. Two measurement techniques, high-speed digital image correlation and a crack propagation gauge, were applied to acquire real-time crack locations and crack propagating velocities of NSCB samples under various dynamic loads. Macroscopic failure data were verified via our modified rate-dependent theoretical model for the prediction of crack deflection and penetration. Then the typical parameter, joint roughness coefficient (JRC), was used to characterise the micro-features of each fracture surface at different loading rates. This parameter is quantified in terms of the fractal dimension through our image processing method. In light of the comparisons of three scenarios under different degrees of dynamic loading, the JRC values linearly decrease with loading rate, which is attributed to the predominant failure pattern of microscopic grains changing from deflection to penetration. In addition, micro-grains in larger size on fracture surface roughness are more sensitive to the increase of loading rate, e.g. in rock, resulting in a greater decrease of fracture surface roughness with respect to that in cement with small micro-grains. However, if the crack propagation velocity exceeds the critical value that contributing to the micro-cracks branching, the declined fracture surface roughness will increase monotonically with the loading rate. The results help to predict the failure pattern of two-phase structures in both quasi-static and dynamic conditions as well allowing quantitative analysis of fracture surface morphology under dynamic load.

@article{
 title = {Rate effect on crack propagation measurement results with crack propagation gauge, digital image correlation, and visual methods},
 type = {article},
 year = {2019},
 keywords = {Crack propagation gauge,Digital image correlation,Fracture process zone,Rate dependent,Rock material},
 pages = {106537},
 volume = {219},
 websites = {https://linkinghub.elsevier.com/retrieve/pii/S0013794419303522},
 month = {10},
 id = {d968a0c8-2016-38c9-8c31-0cdd8eb99a68},
 created = {2022-02-23T16:55:59.111Z},
 file_attached = {true},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2025-03-13T16:56:55.997Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Ju2019},
 folder_uuids = {ae2757ab-34eb-461b-b313-4d85729d6f10},
 private_publication = {false},
 abstract = {The rate-dependent measurement gaps among the crack propagation gauge (CPG), digital image correlation (DIC), and Visual methods for measuring dynamic rock crack propagation were determined using a case study. Dynamic notched semi-circular bending (NSCB) tests of a rock material, namely, red sandstone, were conducted using a modified split Hopkinson pressure bar system to form different crack propagating velocities (CPVs). From the viewpoint of the initial crack time, a normal strain threshold of 2% in the DIC was effective in obtaining a match between the CPG and DIC methods at a low CPV. However, the selected 2%–5% normal strains in the DIC were pivotal factors that could compromise the results from the CPG and Visual methods with a low CPV in terms of the peak CPV, whereas 2%–3% normal strains were recommended for cases with a high CPV. In addition, the equivalent crack-velocity-dependent strain thresholds (tiDIC equal to tiCPG and tiDIC equal to tiVisual) for the CPG, Visual, and DIC techniques displayed a linear fit with the CPV. The measurement gap between the DIC and Visual methods was narrower than the measurement gap between the DIC and CPG methods. The critical initial crack time of CPG for red sandstone needed the condition of a CPV of approximately 500 m/s. A potential explanation for these gaps was proposed in terms of the changes in the fracture process zone with CPV, and three suggestions were subsequently recommended based on the experimental results to aid in the interpretation of other experimental results.},
 bibtype = {article},
 author = {Ju, Minghe and Li, Jianchun and Yao, Qiangling and Li, Xiaofeng and Zhao, Jian},
 doi = {10.1016/j.engfracmech.2019.106537},
 journal = {Engineering Fracture Mechanics}
}

The rate-dependent measurement gaps among the crack propagation gauge (CPG), digital image correlation (DIC), and Visual methods for measuring dynamic rock crack propagation were determined using a case study. Dynamic notched semi-circular bending (NSCB) tests of a rock material, namely, red sandstone, were conducted using a modified split Hopkinson pressure bar system to form different crack propagating velocities (CPVs). From the viewpoint of the initial crack time, a normal strain threshold of 2% in the DIC was effective in obtaining a match between the CPG and DIC methods at a low CPV. However, the selected 2%–5% normal strains in the DIC were pivotal factors that could compromise the results from the CPG and Visual methods with a low CPV in terms of the peak CPV, whereas 2%–3% normal strains were recommended for cases with a high CPV. In addition, the equivalent crack-velocity-dependent strain thresholds (tiDIC equal to tiCPG and tiDIC equal to tiVisual) for the CPG, Visual, and DIC techniques displayed a linear fit with the CPV. The measurement gap between the DIC and Visual methods was narrower than the measurement gap between the DIC and CPG methods. The critical initial crack time of CPG for red sandstone needed the condition of a CPV of approximately 500 m/s. A potential explanation for these gaps was proposed in terms of the changes in the fracture process zone with CPV, and three suggestions were subsequently recommended based on the experimental results to aid in the interpretation of other experimental results.

@article{
 title = {Damage assessment and blast vibrations controlling considering rock properties of underwater blasting},
 type = {article},
 year = {2019},
 keywords = {Geological structure,Ground vibration,PPV prediction,Rock property,Underwater blasting},
 pages = {1-16},
 volume = {121},
 id = {8823d192-3c48-332b-ba93-f8586d172d79},
 created = {2022-02-23T16:55:59.135Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2023-10-12T02:55:29.084Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Li2019o},
 private_publication = {false},
 abstract = {Underwater drilling blasting has significant vibrational attenuation effects compared to deep-hole blasting. The aim of this study is to propose a novel model for predicting peak particle velocity (PPV) considering the effects of the geological factor (i.e., weathering state), rock properties (i.e., rock quality designation) and engineering category (i.e., blasting on land or underwater) on the attenuation of the ground vibrations and frequency. A series of blasting experiments distributed over five sites were performed in the dredging engineering of the waterway at the Taishan Nuclear Power Plant. The geological investigation and the laboratory rock testing show that the weathering degree of the rock mass results in exponential increase in geological parameter α and linear increase in attenuation coefficientβ. The impact of the high rock quality designation (RQD) puts limitations on the PPV attenuation, particularly for ground vibration induced by underwater blasting. The experimental results show that PPVs underestimated by the conventional equation (with a correlation coefficient of 64%) increase the risk of potential damage for protected objects. The novel predictor, formed by adding the depth ratio of the water to the scaled distance law suggested by Duvall and Fogelson, is verified by the agreement of the measurement data in this case with a correlation coefficient of 92%. Additionally, the frequency spectrum characteristics observed from blasting either on land or underwater are discussed. High-frequency components are found to be highly filtered due to the water sloshing underwater.},
 bibtype = {article},
 author = {Li, X. F. and Li, H. B. and Zhang, G. K.},
 doi = {10.1016/j.ijrmms.2019.06.004},
 journal = {International Journal of Rock Mechanics and Mining Sciences},
 number = {April}
}

Underwater drilling blasting has significant vibrational attenuation effects compared to deep-hole blasting. The aim of this study is to propose a novel model for predicting peak particle velocity (PPV) considering the effects of the geological factor (i.e., weathering state), rock properties (i.e., rock quality designation) and engineering category (i.e., blasting on land or underwater) on the attenuation of the ground vibrations and frequency. A series of blasting experiments distributed over five sites were performed in the dredging engineering of the waterway at the Taishan Nuclear Power Plant. The geological investigation and the laboratory rock testing show that the weathering degree of the rock mass results in exponential increase in geological parameter α and linear increase in attenuation coefficientβ. The impact of the high rock quality designation (RQD) puts limitations on the PPV attenuation, particularly for ground vibration induced by underwater blasting. The experimental results show that PPVs underestimated by the conventional equation (with a correlation coefficient of 64%) increase the risk of potential damage for protected objects. The novel predictor, formed by adding the depth ratio of the water to the scaled distance law suggested by Duvall and Fogelson, is verified by the agreement of the measurement data in this case with a correlation coefficient of 92%. Additionally, the frequency spectrum characteristics observed from blasting either on land or underwater are discussed. High-frequency components are found to be highly filtered due to the water sloshing underwater.

@article{
 title = {单裂隙花岗岩破坏强度及裂纹扩展特征研究},
 type = {article},
 year = {2019},
 keywords = {18,acoustic emission,crack propagation,failure strength,ganne 等,hypocenter distribution,p,rock mechanics,基于声发射测试研,结聚合的临界值},
 volume = {38},
 id = {0ddf0cae-de5f-3822-abf3-4ec8d081267d},
 created = {2022-02-23T16:59:37.912Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2023-10-12T02:55:29.355Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {2019b},
 source_type = {JOUR},
 private_publication = {false},
 bibtype = {article},
 author = {张国凯, undefined and 李海波, undefined and 王明洋, undefined and 李晓锋, undefined},
 journal = {岩石力学与工程学报},
 number = {51809137}
}

@article{
 title = {Grain-Based Discrete Element Method (GB-DEM) Modelling of Multi-scale Fracturing in Rocks Under Dynamic Loading},
 type = {article},
 year = {2018},
 keywords = {Dynamic fracturing,Failure mechanisms,Grain-based DEM,Micro-fracturing,Realistic micro-heterogeneity,Strain rate},
 pages = {3785-3817},
 volume = {51},
 month = {12},
 day = {20},
 id = {acbd266c-c8c2-34a7-9d75-218976b7d124},
 created = {2021-07-02T10:59:14.917Z},
 file_attached = {true},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2022-02-23T17:05:51.499Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Li2018l},
 source_type = {JOUR},
 notes = {施引文献 :3<br/><br/>Export Date: 15 May 2019},
 folder_uuids = {8f85d7cb-0cf0-454b-9566-6fac9d32146f},
 private_publication = {false},
 abstract = {This study aims to explore dynamic behaviours of fracturing and damage evolution of rock materials at the grain scale. A grain-based discrete element method (GB-DEM) is proposed to reveal microscale characterisation and mineral grain compositions of rock materials realistically. Micro-parameters of GB-DEM are obtained by calibrating quasi-static strengths, elastic modulus, stress–strain curves, and fracture characteristics of igneous rocks. Comprehensive numerical simulations are conducted to compare with dynamic experimental results obtained by the split Hopkinson pressure bar (SHPB). The reasonability of using the GB-DEM is presented to validate fundamental pre-requisites of the SHPB technique. Combined with crack strain and acoustic emissions, the rate dependency of crack initiation stress threshold and crack damage stress threshold is investigated. The dynamic damage evolution in the form of Weibull distribution is distinctively different from that in static tests and the shape/scale parameters are presented as functions of strain rate. Moreover, microcharacteristics of crack fracturing transition and fracturing patterns formation are discussed in detail. It is found that there exist two classes of mechanical behaviour (i.e., Class I and Class II) observed from stress–strain responses of dynamic tests. Main fracturing surfaces induced by intergranular fractures split the specimen along the direction of stress wave propagation in the type of Class I behaviour. Branching cracks derive the cracks’ nucleation and in turn increases the fragment degree. A shearing band formed near the fracture surface is caused by grain pulverisations, which eventually enhances the sustainability of rocks under dynamic loading. At last, we propose a generalised equation of dynamic increase factor in the range from 10− 5 to 500/s, and also discuss the characteristic strain rate.},
 bibtype = {article},
 author = {Li, X. F. and Zhang, Q. B. and Li, H. B. and Zhao, J.},
 doi = {10.1007/s00603-018-1566-2},
 journal = {Rock Mechanics and Rock Engineering},
 number = {12}
}

This study aims to explore dynamic behaviours of fracturing and damage evolution of rock materials at the grain scale. A grain-based discrete element method (GB-DEM) is proposed to reveal microscale characterisation and mineral grain compositions of rock materials realistically. Micro-parameters of GB-DEM are obtained by calibrating quasi-static strengths, elastic modulus, stress–strain curves, and fracture characteristics of igneous rocks. Comprehensive numerical simulations are conducted to compare with dynamic experimental results obtained by the split Hopkinson pressure bar (SHPB). The reasonability of using the GB-DEM is presented to validate fundamental pre-requisites of the SHPB technique. Combined with crack strain and acoustic emissions, the rate dependency of crack initiation stress threshold and crack damage stress threshold is investigated. The dynamic damage evolution in the form of Weibull distribution is distinctively different from that in static tests and the shape/scale parameters are presented as functions of strain rate. Moreover, microcharacteristics of crack fracturing transition and fracturing patterns formation are discussed in detail. It is found that there exist two classes of mechanical behaviour (i.e., Class I and Class II) observed from stress–strain responses of dynamic tests. Main fracturing surfaces induced by intergranular fractures split the specimen along the direction of stress wave propagation in the type of Class I behaviour. Branching cracks derive the cracks’ nucleation and in turn increases the fragment degree. A shearing band formed near the fracture surface is caused by grain pulverisations, which eventually enhances the sustainability of rocks under dynamic loading. At last, we propose a generalised equation of dynamic increase factor in the range from 10− 5 to 500/s, and also discuss the characteristic strain rate.

@article{
 title = {Dynamic fragmentation of rock material: Characteristic size, fragment distribution and pulverization law},
 type = {article},
 year = {2018},
 keywords = {Dynamic fragmentation,Fragment size,High strain rate,Pulverization,Rocks},
 pages = {739-759},
 volume = {199},
 id = {f549d853-b9dc-3629-98e4-08a95b0092fb},
 created = {2022-02-23T16:55:58.816Z},
 file_attached = {true},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2022-02-23T17:05:51.453Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Li2018h},
 folder_uuids = {8f85d7cb-0cf0-454b-9566-6fac9d32146f,89c737c3-3080-497a-9e42-aeafdad30ca7},
 private_publication = {false},
 abstract = {In this study, the dynamic fragmentation of granites at strain rates of 40–150/s is explored by using SHPB apparatus. Two mechanical classes (i.e. class I and class II) are observed from the stress vs. strain curves in high strain rate loading and the transition strain rate separated the two regimes is about 80/s. The samples are pervasively shattered when the strain rate exceeds the transition threshold and the dissipated energy density is as high as 2.0 J/cm3. Fragment size/mass distributions are quantified using image processing technique and Weibull distribution, which provide better agreements with experimental results. Then a novel energy-based fragmentation model for describing the cylindrical samples compacted by single direction impact is proposed to reasonably predict the characteristic fragment size. The compression kinetic energy item explains the catastrophic fracturing, which is a result of multi-dimensional breakage at high strain rate. The class I loading, described as ‘strain energy controlled regime’ produces larger-size, less-number debris and behaved as strain rate independent. The class II loading is kinetic energy controlled which results in pulverized debris and rate dependent failure strength.},
 bibtype = {article},
 author = {Li, X. F. and Li, H. B. and Zhang, Q. B. and Jiang, J. L. and Zhao, J.},
 doi = {10.1016/j.engfracmech.2018.06.024},
 journal = {Engineering Fracture Mechanics}
}

In this study, the dynamic fragmentation of granites at strain rates of 40–150/s is explored by using SHPB apparatus. Two mechanical classes (i.e. class I and class II) are observed from the stress vs. strain curves in high strain rate loading and the transition strain rate separated the two regimes is about 80/s. The samples are pervasively shattered when the strain rate exceeds the transition threshold and the dissipated energy density is as high as 2.0 J/cm3. Fragment size/mass distributions are quantified using image processing technique and Weibull distribution, which provide better agreements with experimental results. Then a novel energy-based fragmentation model for describing the cylindrical samples compacted by single direction impact is proposed to reasonably predict the characteristic fragment size. The compression kinetic energy item explains the catastrophic fracturing, which is a result of multi-dimensional breakage at high strain rate. The class I loading, described as ‘strain energy controlled regime’ produces larger-size, less-number debris and behaved as strain rate independent. The class II loading is kinetic energy controlled which results in pulverized debris and rate dependent failure strength.

@article{
 title = {Dynamic tensile behaviours of heterogeneous rocks: The grain scale fracturing characteristics on strength and fragmentation},
 type = {article},
 year = {2018},
 keywords = {DEM simulation,Dynamic tensile strength,Granular rocks,Micro fracturing,Strain rate effect},
 pages = {98-118},
 volume = {118},
 month = {8},
 id = {1c05212e-35cd-3169-a350-976193dc14e2},
 created = {2022-02-23T16:55:59.122Z},
 file_attached = {true},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2022-02-23T17:05:51.768Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Li2018q},
 folder_uuids = {8f85d7cb-0cf0-454b-9566-6fac9d32146f,78201eac-8ef2-4d3b-927d-dc37446c5be5,89c737c3-3080-497a-9e42-aeafdad30ca7},
 private_publication = {false},
 abstract = {The dynamic tension behaviours of granites are tested with the split Hopkinson pressure bar and the quasi-static responses including the compression and Brazilian splitting are carried out with a material testing system. The experimental results show the tensile strengths behave significant strain rate effect. In order to characterize the realistic fracturing process from the viewpoint of grain scale failure, a multiple scale discrete element model considering the micro heterogeneity is proposed using the digital image processing of mineral scanning for rocks. Comparison of the experimental and numerical tension stress as well as the ultimate fragment state indicates the grain-based model is reasonable in simulation of dynamic tension test on granites. Then the three-wave superposition, crack propagation sequences, end forces and the stress distribution are discussed to confirm the stress equilibrium in the specimen. Using the microheterogeneous model, the micro fracturing process and fragmentation in association with energy dissipation at different strain rates are discussed. It is found that the failure sequence can be divided into five stages as crack initiation, propagation, coalesce, branching and indentation crush on the stress curve in dynamic loading. The intrinsic mechanism of the strain rate effect is believed to be the transitions of the micro fracturing type, orientation and the damage degree in the specimen and in turn exhibiting more energy dissipation as well as fragmentation transition from sparse fracture to pervasive pulverization. Finally, the scaling model of the dynamic increase factor for granite is derived and the characteristic strain rate, increase rate factor values are discussed.},
 bibtype = {article},
 author = {Li, X. F. and Li, X. and Li, H. B. and Zhang, Q. B. and Zhao, J.},
 doi = {10.1016/j.ijimpeng.2018.04.006},
 journal = {International Journal of Impact Engineering},
 number = {April}
}

The dynamic tension behaviours of granites are tested with the split Hopkinson pressure bar and the quasi-static responses including the compression and Brazilian splitting are carried out with a material testing system. The experimental results show the tensile strengths behave significant strain rate effect. In order to characterize the realistic fracturing process from the viewpoint of grain scale failure, a multiple scale discrete element model considering the micro heterogeneity is proposed using the digital image processing of mineral scanning for rocks. Comparison of the experimental and numerical tension stress as well as the ultimate fragment state indicates the grain-based model is reasonable in simulation of dynamic tension test on granites. Then the three-wave superposition, crack propagation sequences, end forces and the stress distribution are discussed to confirm the stress equilibrium in the specimen. Using the microheterogeneous model, the micro fracturing process and fragmentation in association with energy dissipation at different strain rates are discussed. It is found that the failure sequence can be divided into five stages as crack initiation, propagation, coalesce, branching and indentation crush on the stress curve in dynamic loading. The intrinsic mechanism of the strain rate effect is believed to be the transitions of the micro fracturing type, orientation and the damage degree in the specimen and in turn exhibiting more energy dissipation as well as fragmentation transition from sparse fracture to pervasive pulverization. Finally, the scaling model of the dynamic increase factor for granite is derived and the characteristic strain rate, increase rate factor values are discussed.

@article{
 title = {基于声学测试和摄像技术的单裂隙岩石 裂纹扩展特征研究},
 type = {article},
 year = {2018},
 keywords = {acoustic emission,crack propagation,rock mechanics,rock-like material,ultrasonic velocity},
 id = {f07f8e8a-dfa2-3025-9b9d-055e4a6c6769},
 created = {2022-02-23T16:59:37.854Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2023-10-12T02:55:29.257Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {false},
 hidden = {false},
 private_publication = {false},
 bibtype = {article},
 author = {张国凯, undefined and 李海波, undefined and 王明洋, undefined and 李晓锋, undefined},
 number = {51809137}
}

@article{
 title = {Dynamic properties and fracture characteristics of rocks subject to impact loading},
 type = {article},
 year = {2017},
 keywords = {Dynamic damage and fragment,Micro discrete element method,Rate dependency,Rock mechanics,Split Hopkinson pressure bar(SHPB)},
 pages = {2393-2405},
 volume = {36},
 id = {4d289007-34a3-3f32-a48e-1ff5f8a494ea},
 created = {2019-06-30T09:07:18.334Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2021-11-14T01:17:49.894Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Li2017b},
 folder_uuids = {89c737c3-3080-497a-9e42-aeafdad30ca7},
 private_publication = {false},
 abstract = {Split Hopkinson pressure bar(SHPB) apparatus was used to study the factor of dynamic strength increasing, the density of dissipation energy and the fragment size of limestone, dolomite and sandstone subject to impact loading. SHPB has some difficulties to measure the higher strain rate and dynamic damage process for rock materials. The grain-based model was thus built by using the high resolution scanning and image processing technique combined with the discrete element method. The accuracy of numerical simulation was verified with the experimental SHPB results. The results indicated that the dynamic failure strength of rock material was rate dependent strongly, but the elastic modulus did not increase significantly with the increasing strain rate. The semi-empirical formula for evaluating the factor of dynamic strength increasing is consistent with the Ханукаев equation. The failure pattern of the rock transforms from the intact→splitting damage→pulverized damage with the increasing strain rate. This phenomenon is determined by the number of the micro cracks activated and the interaction between the cracks. The increase of the crack density and the change of the crack propagation path are the mechanism of the dynamic fracture of the rock, and the macrosopic responses are the rate effect and fragmentation of the material.},
 bibtype = {article},
 author = {Li, Xiaofeng and Li, Haibo and Liu, Kai and Zhang, Qianbing and Zou, Fei and Huang, Lixing and Zhao, Jian},
 doi = {10.13722/j.cnki.jrme.2017.0539},
 journal = {Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering},
 number = {10}
}

Split Hopkinson pressure bar(SHPB) apparatus was used to study the factor of dynamic strength increasing, the density of dissipation energy and the fragment size of limestone, dolomite and sandstone subject to impact loading. SHPB has some difficulties to measure the higher strain rate and dynamic damage process for rock materials. The grain-based model was thus built by using the high resolution scanning and image processing technique combined with the discrete element method. The accuracy of numerical simulation was verified with the experimental SHPB results. The results indicated that the dynamic failure strength of rock material was rate dependent strongly, but the elastic modulus did not increase significantly with the increasing strain rate. The semi-empirical formula for evaluating the factor of dynamic strength increasing is consistent with the Ханукаев equation. The failure pattern of the rock transforms from the intact→splitting damage→pulverized damage with the increasing strain rate. This phenomenon is determined by the number of the micro cracks activated and the interaction between the cracks. The increase of the crack density and the change of the crack propagation path are the mechanism of the dynamic fracture of the rock, and the macrosopic responses are the rate effect and fragmentation of the material.

@article{
 title = {3D polycrystalline discrete element method (3PDEM) for simulation of crack initiation and propagation in granular rock},
 type = {article},
 year = {2017},
 keywords = {3D polycrystalline discrete element method,Damage propagation,Discontinuum,Granular rock,Numerical modeling},
 pages = {96-112},
 volume = {90},
 id = {7dbe3729-20ea-356b-9601-178b257224f2},
 created = {2019-12-12T16:02:50.639Z},
 file_attached = {true},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2022-02-23T16:59:41.836Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Li2017a},
 folder_uuids = {8f85d7cb-0cf0-454b-9566-6fac9d32146f,78201eac-8ef2-4d3b-927d-dc37446c5be5,89c737c3-3080-497a-9e42-aeafdad30ca7},
 private_publication = {false},
 abstract = {A three-dimensional Voronoi tessellation model based on the distinct element method (DEM) is proposed to model the representative part of the microstructures of granular brittle rocks. Regularization is employed to decrease the frequency of polyhedrons with large edge ratio and contributes to a higher efficiency for element meshing. Sensitivity analyses are performed for a series of micro contact parameters in accordance with the macro responses observed in laboratory experiments (e.g. the uniaxial compression test, the Brazilian disc test and the triaxial compression test). Verifications by simulating the spalling test and plate impact test indicate that the 3D polycrystalline discrete element method (3PDEM) can be employed for efficiently simulating nonlinear mechanical behaviors, large deformation, strain softening and rock dynamics.},
 bibtype = {article},
 author = {Li, X. F. and Li, H. B. and Zhao, J.},
 doi = {10.1016/j.compgeo.2017.05.023},
 journal = {Computers and Geotechnics}
}

A three-dimensional Voronoi tessellation model based on the distinct element method (DEM) is proposed to model the representative part of the microstructures of granular brittle rocks. Regularization is employed to decrease the frequency of polyhedrons with large edge ratio and contributes to a higher efficiency for element meshing. Sensitivity analyses are performed for a series of micro contact parameters in accordance with the macro responses observed in laboratory experiments (e.g. the uniaxial compression test, the Brazilian disc test and the triaxial compression test). Verifications by simulating the spalling test and plate impact test indicate that the 3D polycrystalline discrete element method (3PDEM) can be employed for efficiently simulating nonlinear mechanical behaviors, large deformation, strain softening and rock dynamics.

@inproceedings{
 title = {Numerical simulation of rock dynamic damage at high strain rates},
 type = {inproceedings},
 year = {2017},
 id = {75f98bdf-b26c-314c-aab1-9c5cbf2f1208},
 created = {2021-11-09T21:14:58.685Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2021-11-14T01:17:49.832Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Li2017j},
 source_type = {CONF},
 private_publication = {false},
 bibtype = {inproceedings},
 author = {Li, Xiaofeng and Li, Haibo and Liu, Kai and Ju, Minghe},
 booktitle = {6th International Conference on Design and Analysis of Protective Structures (DAPS 2017)}
}

@article{
 title = {冲击荷载作用下岩石动态力学特性及破裂 特征研究},
 type = {article},
 year = {2017},
 keywords = {13-14,dynamic damage and fragment,method,micro discrete element,olsson 等,rate dependency,rock mechanics,shpb,split hopkinson pressure bar,通过对凝灰岩进行 shpb 冲击试验},
 volume = {36},
 id = {a93bbac8-6776-3841-8801-a4417340aee8},
 created = {2022-02-23T16:59:38.246Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2023-10-12T02:55:29.024Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {false},
 hidden = {false},
 private_publication = {false},
 bibtype = {article},
 author = {李晓锋, undefined and 李海波, undefined and 张乾兵, undefined and Jian, Zhao},
 number = {10}
}

@article{
 title = {Application of coupled analysis methods for prediction of blast-induced dominant vibration frequency},
 type = {article},
 year = {2016},
 keywords = {dimensional analysis,dominant vibration frequency,grey relational analysis,prediction,sensitivity analysis},
 pages = {153-162},
 volume = {15},
 id = {bce79342-9cd1-361b-aa57-b76e4eb75725},
 created = {2019-06-30T09:07:18.158Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2021-11-14T01:17:50.103Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Li2016g},
 private_publication = {false},
 abstract = {Blast-induced dominant vibration frequency (DVF) involves a complex, nonlinear and small sample system considering rock properties, blasting parameters and topography. In this study, a combination of grey relational analysis and dimensional analysis procedures for prediction of dominant vibration frequency are presented. Six factors are selected from extensive effect factor sequences based on grey relational analysis, and then a novel blast-induced dominant vibration frequency prediction is obtained by dimensional analysis. In addition, the prediction is simplified by sensitivity analysis with 195 experimental blast records. Validation is carried out for the proposed formula based on the site test database of the firstperiod blasting excavation in the Guangdong Lufeng Nuclear Power Plant (GLNPP). The results show the proposed approach has a higher fitting degree and smaller mean error when compared with traditional predictions.},
 bibtype = {article},
 author = {Li, Haibo and Li, Xiaofeng and Li, Jianchun and Xia, Xiang and Wang, Xiaowei},
 doi = {10.1007/s11803-016-0312-6},
 journal = {Earthquake Engineering and Engineering Vibration},
 number = {1}
}

Blast-induced dominant vibration frequency (DVF) involves a complex, nonlinear and small sample system considering rock properties, blasting parameters and topography. In this study, a combination of grey relational analysis and dimensional analysis procedures for prediction of dominant vibration frequency are presented. Six factors are selected from extensive effect factor sequences based on grey relational analysis, and then a novel blast-induced dominant vibration frequency prediction is obtained by dimensional analysis. In addition, the prediction is simplified by sensitivity analysis with 195 experimental blast records. Validation is carried out for the proposed formula based on the site test database of the firstperiod blasting excavation in the Guangdong Lufeng Nuclear Power Plant (GLNPP). The results show the proposed approach has a higher fitting degree and smaller mean error when compared with traditional predictions.

@article{
 title = {Numerical simulation of mechanical characteristics of jointed rock in direct shear test},
 type = {article},
 year = {2016},
 keywords = {Crack evolution,Direct shear test,Joint,Jointed rock,Particle flow code},
 pages = {583-591},
 volume = {37},
 id = {df2827cf-e1a5-3cee-b033-bbf1fe84c47d},
 created = {2019-06-30T09:07:18.193Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2021-11-14T01:17:49.478Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Li2016f},
 private_publication = {false},
 abstract = {The stability of rock engineering is strongly dependent on the shear strength of jointed rock mass. Based on the particle flow code (PFC2D), the reasonable mesoscopic parameters are selected in combination with experimental results to analyze the meso-properties of crack propagation, energy transmission, and acoustic emission phenomenon of jointed rock. The strength models and failure patterns of jointed rock are numerically simulated. The main research results are summarized as follows. Abrasive and shear failure patterns heavily exist in jointed rock, and different failure patterns are corresponding to different strength models. Rock mass is damaged along joint plane with the increase of shear deformation. Normal cracks prevail within elastic stage, whereas shear cracks dominate along the rough surface within plastic stage. The joint plane slides owing to appearance of crushed zone induced by the coalescence of R and P cracks. Boundary energy is mainly converted into strain energy and more normal cracks are generated prior to the peak shear strength. With the increase of shear stress, the friction energy grows rapidly and a large amount of shear cracks are produced at the same time. Compared with experiments, PFC2D can be used to simulate the shear properties of jointed rock mass well, which remedies the challenge of simulating behaviors of jointed rock at meso-scale in the laboratory test and provides a useful reference for further research on direct shear tests of jointed rock mass.},
 bibtype = {article},
 author = {Li, Xiao Feng and Li, Hai Bo and Xia, Xiang and Liu, Bo and Feng, Hai Peng},
 doi = {10.16285/j.rsm.2016.02.032},
 journal = {Yantu Lixue/Rock and Soil Mechanics},
 number = {2}
}

The stability of rock engineering is strongly dependent on the shear strength of jointed rock mass. Based on the particle flow code (PFC2D), the reasonable mesoscopic parameters are selected in combination with experimental results to analyze the meso-properties of crack propagation, energy transmission, and acoustic emission phenomenon of jointed rock. The strength models and failure patterns of jointed rock are numerically simulated. The main research results are summarized as follows. Abrasive and shear failure patterns heavily exist in jointed rock, and different failure patterns are corresponding to different strength models. Rock mass is damaged along joint plane with the increase of shear deformation. Normal cracks prevail within elastic stage, whereas shear cracks dominate along the rough surface within plastic stage. The joint plane slides owing to appearance of crushed zone induced by the coalescence of R and P cracks. Boundary energy is mainly converted into strain energy and more normal cracks are generated prior to the peak shear strength. With the increase of shear stress, the friction energy grows rapidly and a large amount of shear cracks are produced at the same time. Compared with experiments, PFC2D can be used to simulate the shear properties of jointed rock mass well, which remedies the challenge of simulating behaviors of jointed rock at meso-scale in the laboratory test and provides a useful reference for further research on direct shear tests of jointed rock mass.

@article{
 title = {Effects of microstructure and micro parameters on macro mechanical properties and failure of rock},
 type = {article},
 year = {2016},
 keywords = {Evolution of cracks,Macro mechanical properties,Micro parameter,Microstructure,Rock mechanics, particle flow code(PFC)},
 pages = {1341-1352},
 volume = {35},
 id = {216e8ce5-df85-376e-bcb2-93ab61f7f43a},
 created = {2019-06-30T09:07:18.284Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2021-11-14T01:17:50.082Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Zhang2016a},
 private_publication = {false},
 abstract = {Clump and cluster models based on two-dimensional particle flow code(PFC2D) were constructed through two different algorithms to explore the effects of micro parameters and microstructure(crystal grain size and distribution, pre-existing cracks) on the macro mechanical properties of specimen and to quantify the relationships between them. Meanwhile, the development of micro cracks and the mechanism of micro failure were studied. It was revealed that two algorithms had their own advantages. Macro mechanical properties of marked circular region algorithm changed with the variation of micro parameters nicely. The composition of crystalline gradation was better controlled by the searching algorithm. The uniaxial compressive strength(UCS) and the tensile strength(TS) are in exponential relationship with the clump radius and un-bonded ratio(random pre-existing cracks) and are in power relationship with the bond strength ratio. The elastic modulus and Poisson's ratio are in linear relationship with the clump radius, bond strength ratio and un-bonded ratio. With the increase of the clump radius, bond strength ratio, bond strength ratio n of cluster and un-bonded ratio, the ratio of uniaxial compressive strength to tensile strength which is mostly affected by bond strength ratio increases a lot. The ratio of tensile cracks is mostly affected by the bond strength ratio, followed by the clump radius. Under the uniaxial compression, the failure of specimen is dominated by the tensile cracks which mainly extend along the axial direction. However, the angle between the dominant orientation of shear cracks and axis is 20 degree to 40 degree. Brazil test failure is dominated by tensile cracks across the center of specimen. The evolution of micro cracks and failure modes are different for cluster and clump models. Compared with the cluster model, the shear crack ratio of clump model is bigger and crack crushing zone is wider. Moreover, the fracture surface is more rough and uneven.},
 bibtype = {article},
 author = {Zhang, Guokai and Li, Haibo and Xia, Xiang and Li, Junru and Li, Xiaofeng and Song, Tao},
 doi = {10.13722/j.cnki.jrme.2015.1154},
 journal = {Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering},
 number = {7}
}

Clump and cluster models based on two-dimensional particle flow code(PFC2D) were constructed through two different algorithms to explore the effects of micro parameters and microstructure(crystal grain size and distribution, pre-existing cracks) on the macro mechanical properties of specimen and to quantify the relationships between them. Meanwhile, the development of micro cracks and the mechanism of micro failure were studied. It was revealed that two algorithms had their own advantages. Macro mechanical properties of marked circular region algorithm changed with the variation of micro parameters nicely. The composition of crystalline gradation was better controlled by the searching algorithm. The uniaxial compressive strength(UCS) and the tensile strength(TS) are in exponential relationship with the clump radius and un-bonded ratio(random pre-existing cracks) and are in power relationship with the bond strength ratio. The elastic modulus and Poisson's ratio are in linear relationship with the clump radius, bond strength ratio and un-bonded ratio. With the increase of the clump radius, bond strength ratio, bond strength ratio n of cluster and un-bonded ratio, the ratio of uniaxial compressive strength to tensile strength which is mostly affected by bond strength ratio increases a lot. The ratio of tensile cracks is mostly affected by the bond strength ratio, followed by the clump radius. Under the uniaxial compression, the failure of specimen is dominated by the tensile cracks which mainly extend along the axial direction. However, the angle between the dominant orientation of shear cracks and axis is 20 degree to 40 degree. Brazil test failure is dominated by tensile cracks across the center of specimen. The evolution of micro cracks and failure modes are different for cluster and clump models. Compared with the cluster model, the shear crack ratio of clump model is bigger and crack crushing zone is wider. Moreover, the fracture surface is more rough and uneven.

@article{
 title = {Macro–meso failure mechanism of soil–rock mixture at medium strain rates},
 type = {article},
 year = {2016},
 keywords = {Compressibility,Deformation,Laboratory test,Soil/rock mechanics},
 pages = {28-33},
 volume = {6},
 id = {6c8704ca-0c8b-3695-ac93-873349ef3614},
 created = {2019-06-30T09:07:18.311Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2022-02-23T17:05:51.872Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Wang2016},
 private_publication = {false},
 abstract = {Uniaxial compressive strength experiments at medium strain rate were conducted to characterise rate effects and the macro–meso failure mechanism of a soil and rock mixture (SRM) with different rock block percentages using a servo-hydraulic variable frequency dynamic machine. Macroscopic failure morphology descriptions and meso three-dimensional laser scanning techniques are used to investigate internal failure mechanism. The results indicated that SRM specimens experience splitting failure, shear failure and conical failure with increasing strain rate. The cumulative fracture width and surface toughness were dependent on the loading rate, which were the results of interaction between rock blocks and the soil matrix and induced by the intrinsic fracture mechanism.},
 bibtype = {article},
 author = {Wang, Y. and Li, X. and Zheng, B. and Zhang, B. and He, J. M. and Li, S. D.},
 doi = {10.1680/jgele.15.00118},
 journal = {Geotechnique Letters},
 number = {1}
}

Uniaxial compressive strength experiments at medium strain rate were conducted to characterise rate effects and the macro–meso failure mechanism of a soil and rock mixture (SRM) with different rock block percentages using a servo-hydraulic variable frequency dynamic machine. Macroscopic failure morphology descriptions and meso three-dimensional laser scanning techniques are used to investigate internal failure mechanism. The results indicated that SRM specimens experience splitting failure, shear failure and conical failure with increasing strain rate. The cumulative fracture width and surface toughness were dependent on the loading rate, which were the results of interaction between rock blocks and the soil matrix and induced by the intrinsic fracture mechanism.

@article{
 title = {Numerical simulation of rock fragmentation mechanisms subject to wedge penetration for TBMs},
 type = {article},
 year = {2016},
 keywords = {Fragmentation,Grain-based rock,Particle flow code,TBM indentation,Wedge indenter},
 pages = {96-108},
 volume = {53},
 id = {1fa68434-45b4-3b3d-9bfe-a3dfd70f219d},
 created = {2019-12-12T16:02:54.477Z},
 file_attached = {true},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2022-02-23T16:59:42.688Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Li2016b},
 folder_uuids = {8f85d7cb-0cf0-454b-9566-6fac9d32146f,89c737c3-3080-497a-9e42-aeafdad30ca7},
 private_publication = {false},
 abstract = {The rock fragmentation mechanism and failure process induced by a wedge indenter for TBMs are numerically simulated utilizing the discrete element method (DEM) in the present study. A novel clustered assembly approach with irregular boundaries for grain-based brittle rock is incorporated into the particle flow code (PFC) to calibrate the macro-responses such as the low tensile to compressive strength ratio observed in laboratory tests. The simulation results are compared with laboratory tests which were conducted to reveal the rock indentation process and rock-tool interactions. The numerical analysis can be divided to two main parts. Part one is to investigate the crack propagation and damage evolution at meso-scale associated with the force-indentation curve. The stress field distributions with respect to indentation time are depicted. It is revealed that the tensile cracks are resulted from the chipping process and the shear cracks are induced by the crushing force with the orientation angle ranging from 45° to 55°, which is in good agreement with macro-observations. In Part two, the fragmentation efficiency and penetration rate under different cases are analyzed with several parameters such as the wedge angle, the confinement stress and the penetration velocity. Meanwhile, the blunt indenter is taken as a special case for analysis and comparison of the fragmentation mechanism.},
 bibtype = {article},
 author = {Li, X. F. and Li, H. B. and Liu, Y. Q. and Zhou, Q. C. and Xia, X.},
 doi = {10.1016/j.tust.2015.12.010},
 journal = {Tunnelling and Underground Space Technology}
}

The rock fragmentation mechanism and failure process induced by a wedge indenter for TBMs are numerically simulated utilizing the discrete element method (DEM) in the present study. A novel clustered assembly approach with irregular boundaries for grain-based brittle rock is incorporated into the particle flow code (PFC) to calibrate the macro-responses such as the low tensile to compressive strength ratio observed in laboratory tests. The simulation results are compared with laboratory tests which were conducted to reveal the rock indentation process and rock-tool interactions. The numerical analysis can be divided to two main parts. Part one is to investigate the crack propagation and damage evolution at meso-scale associated with the force-indentation curve. The stress field distributions with respect to indentation time are depicted. It is revealed that the tensile cracks are resulted from the chipping process and the shear cracks are induced by the crushing force with the orientation angle ranging from 45° to 55°, which is in good agreement with macro-observations. In Part two, the fragmentation efficiency and penetration rate under different cases are analyzed with several parameters such as the wedge angle, the confinement stress and the penetration velocity. Meanwhile, the blunt indenter is taken as a special case for analysis and comparison of the fragmentation mechanism.

@article{
 title = {类节理岩石直剪试验力学特性的数值模拟研究},
 type = {article},
 year = {2016},
 pages = {583-591},
 volume = {37},
 id = {98100db8-54e6-3b74-a1a4-f68634aaafe0},
 created = {2021-11-14T01:17:48.780Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2021-11-14T01:17:48.780Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {2016c},
 source_type = {JOUR},
 private_publication = {false},
 bibtype = {article},
 author = {李晓锋, undefined and 李海波, undefined and 夏祥, undefined and 刘博, undefined and 冯海鹏, undefined},
 journal = {岩土力学},
 number = {2}
}

@inproceedings{
 title = {Dynamic response of rock mass during split Hopkinson pressure bar test: numerical simulation utilizing distinct element method},
 type = {inproceedings},
 year = {2015},
 id = {fe768a7b-ba11-3f7e-a531-f1b9c279dcc4},
 created = {2021-11-09T21:14:58.886Z},
 file_attached = {false},
 profile_id = {b92175f3-f861-3b22-a150-9efbe1405e1e},
 last_modified = {2021-11-14T01:17:49.781Z},
 read = {false},
 starred = {false},
 authored = {true},
 confirmed = {true},
 hidden = {false},
 citation_key = {Li2015e},
 source_type = {CONF},
 private_publication = {false},
 bibtype = {inproceedings},
 author = {Li, Xiaofeng and Li, Haibo and Li, Jianchun},
 booktitle = {The 12th International Conference on Analysis of Discontinuous Deformation (ICADD-12)}
}