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Failure characteristics and fracture mechanism of overburden rock induced by mining:A case study in China

International Journal of Coal Science & Technology 2024年第3期11卷 241-255页

作者： Jiawei Li Meng Zhang Changxiang Wang Changlong Liao Baoliang Zhang Department of Energy and Power Engineering College of Mechanical and Transportation EngineeringChina University of Petroleum(Beijing)BeijingChina Department of Energy and Power Engineering Tsinghua UniversityBeijingChina College of Safety Science and Engineering Anhui University of Science and TechnologyHuainan232000China School of Architecture and Civil Engineering Liaocheng UniversityLiaocheng252000China

This study employs similar simulation testing and discrete element simulation coupling to analyze the failure and deformation processes of a model coal seam's *** caving area of the overburden rock is divided into three zones:the delamination fracture zone,broken fracture zone,and compaction *** caving and fracture zones'heights are approximately 110 m above the coal seam,with a maximum subsidence of 11 *** delamination fracture zone's porosity range is between 0.2 and 0.3,while the remainder of the roof predominantly exhibits a porosity of less than *** addition,the numerical model's stress analysis revealed that the overburden rock's displacement zone forms an'arch-beam'structure starting from 160 m,with the maximum and minimum stress values decreasing as the distance of advancement *** the stress beam interval of the overburden rock,the maximum value changes periodically as the advancement distance *** on a comparative analysis between observable data from on-site work and numerical simulation results,the stress data from the numerical simulation are essentially consistent with the actual results detected on-site,indicating the validity of the numerical simulation results.

关键词： Fracture development characteristics Similar simulation experiment Layer porosity discrete element numerical simulation

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Experimental study on the rock breaking effect of different tooth shapes of inserted teeth in a hobbing-cone hybrid PDC bit under complex stress environment

GEOENERGY SCIENCE AND ENGINEERING

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GEOENERGY SCIENCE AND ENGINEERING 2025年 246卷

作者： Huang, Xin Chang, Jucai Li, Chuanming Yang, Weihao Pang, Jianyong Zou, Jiuqun Zhang, Yu Anhui Univ Sci & Technol Sch Min Engn Huainan 232001 Peoples R China China Univ Min & Technol State Key Lab Geomech & Deep Underground Engn Xuzhou 221116 Peoples R China Anhui Univ Sci & Technol Sch Civil Engn & Architecture Huainan 232001 Peoples R China

The hobbing-cone hybrid PDC bit has emerged with the increasing exploitation of deep oil and gas resources. As an important component of new bits, studying the mechanism of toothed fracturing of deep rocks is crucial for improving rock-breaking efficiency. In this paper, the spherical teeth and conical teeth were used to intrude sandstone under different confining pressures, and the brittleness index (BIm), specific energy (SE), and average fragment size (dm) were used to analyze the rock-breaking effect. The 3D contour scanner quantitatively analyzed the crushing pit area. Finally, the in-situ CT scanning and discrete element numerical simulation were used to summarize the crack propagation law. The results show that with the increase of confining pressure, the BIm of inserted teeth increases continuously, and the growth rate of conical teeth increases, while that of spherical teeth decreases. The SE and dm exhibit a symmetrical distribution with a confining pressure of 10 MPa as the axis of symmetry. When the difference in principal stress is 5 MPa, the SE is the lowest point, the rock-breaking efficiency is the highest, and the corresponding dm is at the highest point, but the curve trend is the opposite. When the stress difference is 5 MPa, it is conducive to propagating surface cracks, thus forming a larger crushing area and the highest rock-breaking efficiency. Based on CT results, the dense particle core is formed near the inserted teeth, and that of the spherical teeth is located below. In contrast, that of the conical teeth is located on the side, which is also the reason for the difference in crack propagation between different tooth shapes.

关键词： Rock-breaking Confining pressure Evaluation indicators In situ CT discrete element numerical simulation

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Deformation Characteristics and Stability Analysis of Soft-Hard Interbedded Tunnels

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GEOTECHNICAL AND GEOLOGICAL ENGINEERING 2025年第3期43卷 1-20页

作者： Hu, Mei-li Wu, Shun-chuan Pu, Shi-jiang Cheng, Hai-yong Ma, Ji-quan Kunming Univ Sci & Technol Coll Land Resources & Engn Kunming 650093 Peoples R China Minist Nat Resources Key Lab Geol Hazard Predict & Geoecol Restorat Pla Kunming 650093 Yunnan Peoples R China

The deformation characteristics and patterns of interbedded tunnels with soft and hard strata significantly differ from those of tunnels in homogeneous surrounding rock, posing substantial challenges to tunnel construction. To address this issue, discrete element numerical software was employed for a systematic analysis of the deformation characteristics and patterns of soft-hard interbedded tunnels. The results indicate that the extent of significant deformation in soft-hard interbedded tunnels depends on the positioning of the soft rock layer. When the thickness of the soft rock layer surpasses the hard rock layer, the displacement and deformation area are large. Except for horizontal interbedded tunnels, all show asymmetric deformation characteristics. At the same layer-thickness ratios, there is no obvious linear relationship between the deformation of the arch crown and sidewall and the variation of the rock dip angle. The plastic damage area in the hard rock layer is smaller than that in the soft rock layer, and the main damage form is tensile fracture. However, the damage form in the soft rock layer is relatively complex, with more shear damage mixed with tensile damage. The results can provide valuable references for the design and construction of soft-hard interbedded tunnels.

关键词： Tunnel engineering Deformation law discrete element numerical simulation Soft-hard interbedded tunnel Destruction forms

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Study on the characteristics particles of coarse grain material in high bench dump

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SCIENTIFIC REPORTS 2024年第1期14卷 1-18页

作者： Cui, Bo Bi, Yuanlong Gu, Tianfeng Han, Kai Northwest Univ Dept Geol State Key Lab Continental Dynam Xian 710069 Peoples R China

Particle shape is an important factor affecting the strength and deformation of coarse materials in dumps. However, conducting research on particle shape in current laboratory experiments, and there exists no classification standard for the particle shape of the dump. Considering the project on high-bench dump in Jiangxi Province, based on the random particle construction method, this study determined the characteristic particles of coarse grain material in the dumping site by combining field investigation results, large-scale direct shear tests, and numerical analysis. Further, the influence mechanism of coarse grain content and characteristic particles on the mechanical characteristics of the dump were analyzed. The results showed that the increase in coarse grain content enhanced the irregularity of particle shape, increased the internal friction angle between particles, and reduced the cohesion of the dump. Moreover, with increase in the normal stress, the shear strength changed from insignificant to gradually enhanced, although the increasing trend slowed down. The constructed random particle model can well solve the effects of occlusion, nesting, and friction between particles that is neglected by the standard spherical particle model, and the fitting degree is better. The particle characteristics of coarse-grain materials in the dump were primarily block, strip, and flake. The three types of shape characteristics under low normal stress did not affect the mechanical properties of the dump. Further, with the increase in normal stress, the stress-strain curve reflected the shape characteristics and content of the dominant characteristics in the dump. Specifically, the block sample exhibited the dominant characteristics and the most content under the same normal stress, followed by the strip sample, with the flake sample exerting the least influence. The research results provide a theoretical basis for long-term safe operation, disaster monitoring, and early war

关键词： High bench dump Large-scale direct shear test Particle construction Characteristic particles discrete element numerical simulation

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Cumulative damage effect on debris slopes under frequent microseisms

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Journal of Mountain Science 2022年第3期19卷 781-797页

作者： YANG Zhong-ping LI Shi-qi TIAN Xin HU Yuan-xin LI Wan-kun School of Civil Engineering Chongqing UniversityChongqing 400045China State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing UniversityChongqing 400044China National Joint Engineering Research Center for Prevention and Control of Environmental Geological Hazards in the TGR Area(Chongqing) Chongqing 400045China Southwest Institute of Chemical Co. Ltd.Chengdu 610200China Extension Project Headquarters of Chongqing Jiangbei International Airport Chongqing 401120China Chongqing Luneng Development(Group)Co. Ltd.Chongqing 401120China

Debris slopes are widely distributed across the Three Gorges Reservoir area in China,and seasonal fluctuations of the water level in the area tend to cause high-frequency microseisms that subsequently induce landslides on such debris *** this study,a cumulative damage model of debris slope with varying slope characteristics under the effects of frequent microseisms was established,based on the accurate definition of slope damage *** cumulative damage behaviour and the mechanisms of slope instability and sliding under frequent microseisms were thus systematically investigated through a series of shaking table tests and discrete element numerical simulations,and the influences of related parameters such as bedrock,dry density and stone content were *** results showed that the instability mode of a debris slope can be divided into a vibration-compaction stage,a crack generation stage,a crack development stage,and an instability *** the action of frequent microseisms,debris slope undergoes the last three stages cyclically,which causes the accumulation to slide out in layers under the synergistic action of tension and shear,causing the slope to become *** are two sliding surfaces as well as the parallel tensile surfaces in the final instability of the debris *** the process of instability,the development trend of the damage accumulation curve remains similar for debris slopes with different ***,the initial vibration compaction effect in the bedrock-free model is stronger than that in the bedrock model,with the overall cumulative damage degree in the former being lower than that of the *** damage degree of the debris slope with high dry density also develops more slowly than that of the debris slope with low dry *** damage development rate of the debris slope does not always decrease with the increase of stone *** damage degree growth rate of the debris slope with the optimal stone

关键词： Cumulative damage Debris slopes Frequent microseisms Shaking table tests discrete element numerical simulation

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Study on the mechanism of coal pillar instability in coal seam sections containing gangue

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PHYSICS AND CHEMISTRY OF THE EARTH 2023年 132卷

作者： Zhang, Junwen Zhang, Yang Song, Zhixiang Wu, Shaokang Fan, Wen-bing Dong, Xukai Yao, Zixiang China Univ Min & Technol Beijing Sch Energy & Min Engn Beijing Peoples R China China Univ Min & Technol Beijing Natl Demonstrat Ctr Expt Safe Coal Min & Geol Gua Beijing 100083 Peoples R China Shaanxi Xiaobadang Min Co LTD Yulin 719000 Peoples R China

The tail entry of the Shanxi Mine No. 10103 working face is a gob-side roadway featuring a 25 m protective coal pillar that contains double-strata gangue. This composition poses a risk of instability and failure, which can endanger personnel safety and mining efficiency. To address this issue, a mechanical model of coal pillars containing gangue was constructed, and a combination of discrete element modeling and engineering monitoring was utilized to reveal the failure mechanism and influencing factors of such coal pillars. The study offers a sound theoretical foundation for the support of coal pillars in gob-side roadways. Through an examination of the friction coefficient (f) of the coal gangue interface in relation to the Barton peak shear strength (tau max), it was determined that coal pillars containing gangue are susceptible to slip instability failure at the coal gangue interface when the normal stress (sigma R) reaches 20 MPa. The stability of coal pillars containing gangue was further analyzed using discrete element numerical simulation software, which identified key factors such as gangue hardness, thickness, location, and number of strata. Utilizing the outcomes of discrete element simulation, the FLAC-PFC coupling model was formulated to meticulously scrutinize the temporal and spatial progression of the deformation of the surrounding rock, as well as the features of its deformation and failure. As a result of this research, the implementation of the grouting cable + through layer bolt anchoring technique is proposed, wherein the bolt is inclined on both sides to traverse through the coal seam and gangue, thereby stabilizing the interface between the two.

关键词： Gangue-containing coal pillar discrete element numerical simulation FLAC-PFC coupling Interface effect Surrounding rock failure

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Study on instability and damage of a loess slope under strong ground motion by numerical simulation

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SOIL DYNAMICS AND EARTHQUAKE ENGINEERING 2022年 152卷 107050-107050页

作者： Chang, Chaoyu Bo, Jingshan Qi, WenHao Qiao, Feng Peng, Da China Earthquake Adm Key Lab Earthquake Engn & Engn Vibrat Inst Engn Mech Harbin 150080 Peoples R China Inst Disaster Prevent Sanhe 065201 Peoples R China

The instability and damage of loess slopes under strong ground motion can be a complicated process, involving sliding, translation, and rotation, which makes the discrete element method as a suitable theory to simulate such a process. Therefore, in this study, the particle flow code (PFC) is developed to simulate the instability and damage process of the loess landslide under strong motion. Based on field investigations and laboratory tests, the detailed identification of mesoscopic parameter was calibrated, and a 2D model was established. The results show that the slope surface tends to amplify the ground motion, resulting in the strong vibration of the soil on the slope surface. The slope shoulder is the position with the largest amplification coefficient of seismic acceleration, which is the key to the instability and failure of the slope. And, under the seismic force, the tensile failure firstly occurs in the slope upper part, and then the accumulation failure occurs in the lower part, finally a shear outlet is formed. Accordingly, high-frequency component of the Fourier spectrum increases with the slope failure. This study highlights the gradual increase in the difference between the first principal stress and the third principal stress, which destroys the inherent cohesive cements between particles, which is the main cause of slope failure under strong motion.

关键词： Loess seismic landslide discrete element numerical simulation Formation mechanism Key controlling factors Instability damage PFC2D

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