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Evaluating the mechanical properties of anisotropic shale containing bedding and natural fractures with discrete element modeling

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International Journal of Coal Science & Technology 2022年第2期9卷 91-106页

作者： Yingjie Li Lihong Song Yuanjun Tang Jianping Zuo dongjie xue School of Mechanics and Civil Engineering China University of Mining and Technology(Beijing)Beijing 100083China

Natural fracture data from one of the Carboniferous shale masses in the eastern Qaidam Basin were used to establish a stochastic model of a discrete fracture network and to perform discrete element simulation research on the size efect and mechanical parameters of *** solutions of fctitious joints in transversely isotropic media were derived,which made it possible for the proposed numerical model to simulate the bedding and natural fractures in shale *** results indicate that there are two main factors infuencing the representative elementary volume(REV)size of a shale *** frst and most decisive factor is the presence of natural fractures in the block *** second is the anisotropy ratio:the greater the anisotropy is,the larger the *** bedding angle has little infuence on the REV size,whereas it has a certain infuence on the mechanical parameters of the rock *** the bedding angle approaches the average orientation of the natural fractures,the mechanical parameters of the shale blocks decrease *** REV representing the mechanical properties of the Carboniferous shale masses in the eastern Qaidam Basin were comprehensively identifed by considering the infuence of bedding and natural *** the numerical model size is larger than the REV,the fractured rock mass discontinuities can be transformed into equivalent continuities,which provides a method for simulating shale with natural fractures and bedding to analyze the stability of a borehole wall in shale.

关键词： Shale Discrete fracture network Natural fracture Anisotropy Discrete element modeling

Creep behavior and permeability evolution of coal pillar dam for underground water reservoir

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International Journal of Coal Science & Technology 2023年第1期10卷 136-141页

作者： Yulong Chen Xianjie Hao dongjie xue Zhe Li Xiaoran Ma State Key Laboratory of Water Resource Protection andUtilization in Coal Mining BeijingChina China University of Mining and Technology BeijingBeijingChina

Using goof as water storage space plays a vital role in the ecological environment and economic development of arid mining areas,while the rock strength and the stability of coal pillars in underground water reservoirs are closely related to creep *** this work,triaxial creep-seepage tests were conducted for coal samples to develop new insights into the creep behavior and permeability *** results showed that the creep deformation and permeability evolution of coal samples exhibit three stages,namely,the compaction hardening stage before the stress threshold,volumetric compaction stage,and volumetric dilatancy *** coal permeability decreases first and then increases with the creep strain and it is well correlated with the variation of volumetric strain.

关键词： Coal Creep Permeability Volumetric strain

CRPA感染死亡患者危险因素分析及NLR值对预后的评估

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智慧健康 2024年第17期10卷 17-20页

作者：李强薛东杰董珍珍肖志忠北京怀柔医院检验科北京101400 北京市怀柔区疾病预防控制中心微生物科北京101400

目的分析碳青霉烯类耐药铜绿假单胞菌(CRPA)感染患者的临床特征及预后危险因素。方法收集2018年1月—2023年5月本院收治的131例确定为CRPA感染患者的临床资料和实验室数据,根据首次从患者体内分离出CRPA后的30d内的生存状态,最终将患者... 详细信息

目的分析碳青霉烯类耐药铜绿假单胞菌(CRPA)感染患者的临床特征及预后危险因素。方法收集2018年1月—2023年5月本院收治的131例确定为CRPA感染患者的临床资料和实验室数据,根据首次从患者体内分离出CRPA后的30d内的生存状态,最终将患者分为死亡组(38例)和幸存组(93例)。对患者的危险因素进行分析,对NLR值发热预后进行评估。结果死亡组CRPA感染科室分布以ICU为主,幸存组CRPA感染科室分布以呼吸科、神经外科、ICU为主,呼吸科、神经外科、ICU分布情况,差异有统计学意义(P<0.05);在死亡组中,菌株对哌拉西林/他唑巴坦、头孢他啶以及头孢吡肟的耐药率呈现出较高水平;而在幸存组中,对环丙沙星、左氧氟沙星以及哌拉西林/他唑巴坦的耐药率相对较高。特别值得注意的是,哌拉西林/他唑巴坦以及头孢吡肟在两组之间的耐药率差异,经统计分析后显示差异有统计学意义(P<0.05);入住ICU、合并曲霉菌感染及CRPA血流感染是CRPA感染死亡的独立危险因素(P<0.05)。结论我院CRPA感染住院患者发生血流感染、合并曲霉菌感染以及入住ICU是高死亡率的独立危险因素,NLR值对预测CRPA感染患者预后有一定的临床应用价值。

关键词：碳青霉烯类耐药铜绿假单胞菌中性粒细胞与淋巴细胞比值受试者工作特征曲线危险因素

Numerical simulation of gas flow process in mining-induced crack network

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International Journal of Mining Science and Technology 2012年第6期22卷 793-799页

作者： Zhou Hongwei Liu Jinfeng xue dongjie Yi Haiyang xue Junhua State Key Laboratory of Coal Resources and Safe Mining China University of Mining & Technology State Key Laboratory of Deep Coal Mining and Environmental Protection Huainan Mining Group Corporation

The exploitation of coal bed methane or coal gas is one of the most effective solutions of the problem of coal gas hazard.A better understanding of gas flow in mining-induced cracks plays an important role in comprehensive development and utilization of coal gas as well as prevention of coal gas *** paper presents a case study of gas flow in mining-induced crack network regarding the situation of low permeability of coal seam.A two-dimensional physical model is constructed on the basis of geological background of mining face No.1122(1) in coal seam No.11-2,Zhangji Coal Mine,Huainan Mining Group *** mining-induced stress and cracks in overburden rocks are obtained by simulating an extraction in physical *** evolution of mining-induced cracks in the process of advancing of coal mining face is characterized and three typical crack networks are taken from digital photos by means of image ***,the numerical software named COMSOL Multiphysics is employed to simulate the process of gas flow in three representative crack *** of gas pressure at various times in mining-induced crack networks are plotted,suggesting a shape and dimension of gas accumulation area.

关键词： Gas flow Gas pressure Physical modeling Mining-induced cracks COMSOL

Prediction of fracture and dilatancy in granite using acoustic emission signal cloud

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Journal of Rock Mechanics and Geotechnical Engineering 2021年第5期13卷 1059-1077页

作者： dongjie xue Lan Lu Lie Gao Lele Lu Cheng Chen School of Mechanics and Civil Engineering China University of Mining and TechnologyBeijing100083China State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing UniversityChongqing400030China Key Laboratory of Safety and High-efficiency Coal Mining Anhui University of Science and TechnologyHuainan232001China

The invisibility of fracture network evolution in the rock under triaxial compression seriously restricts the correlation modeling between dilatancy behavior and fracture *** key to solving such a challenge is strongly dependent on the accurate modeling of the spatial correlation in fracture network,which could be indirectly re-constructed by the acoustic emission(AE)signal *** the interaction of local fractures,a cube cluster approach is established to describe the spatial *** evolutional cube clusters effectively present the geometric characteristics induced by the increasing dilatancy of *** descriptors(***-axis length sum and pore fraction)are introduced to correlate cluster model with dilatancy *** fitting results support the linear correlation between two descriptors and volumetric strain,which verifies the sensitiveness of the cube cluster model to *** importantly,by the statistical analysis of cluster structure,the cluster model shows the potential of calculating fracture ***,a comparison between dilatancybased damage and porosity-based damage is made not to prove the best but provide an AE-based prediction of local damage ***,four classical models for calculating fracture angle are *** deviations prove the huge difficulty of describing the development of the fracture network uniquely dependent on a fracture *** proximity of measured angle and cluster-based angle supports the effectiveness of predication by the cube cluster approach.

关键词： Fracture network Acoustic emission(AE) Spatial correlation Dilatancy Damage Fracture angle

On the excavation-induced stress drop in damaged coal considering a coupled yield and failure criterion

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International Journal of Coal Science & Technology 2020年第1期7卷 58-67页

作者： dongjie xue Jie Zhou Yintong Liu Lie Gao School of Mechanics and Civil Engineering China University of Mining and TechnologyBeijing 100083China State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing UniversityChongqing 400030China Key Laboratory of Safety and High-Efficiency Coal Mining Anhui University of Science and TechnologyHuainan 232001China

Investigating the stress drop of abutment pressure is the key to a deep quantitative analysis of the discontinuous stress redistribution under *** the present study,uniaxial and triaxial compression tests are carried out separately to determine the bulk and shear moduli,the cohesion,and the internal friction angle of the coal *** extending the meaning of Mohr’s circle referring to yield stress instead of the maximum principal stress,a yield line is introduced to illustrate the stress drop of Mohr’s circle referring to yield stress instead of the maximum principal stress at the elastoplastic ***,a theoretical solution of the stress drop as a function of the damage is proposed to investigate how the abutment pressure differs considering the yield line and failure *** addition,applying the stress drop at the yield line in non-pillar mining,top coal mining,and protective coal mining shows that the damage has a nonlinearly positive influence on the stress *** results shows that the bulk modulus and internal friction angle have a more sensitive influence on the stress drop than do the shear modulus and ***,the stress drop is divided into a discontinuous stress drop at the yield line and a structural stress drop at the failure *** stress drop is effective in describing the discontinuous stress redistribution and shows a clear difference in the movement direction of Mohr’s circle considering the unloading pressure.

关键词： Stress drop Abutment pressure Mohr's circle Yield line Failure line

Cluster modeling of the short-range correlation of acoustically emitted scattering signals

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International Journal of Coal Science & Technology 2021年第4期8卷 575-589页

作者： dongjie xue Lele Lu Jie Zhou Lan Lu Yintong Liu School of Mechanics and Civil Engineering China State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing UniversityChongqing 400030China Key Laboratory of Safety and High-efficiency Coal Mining Anhui University of Science and TechnologyHuainan 232001China

As a widely used measurement technique in rock mechanics,spatial correlation modeling of acoustic emission(AE)scattering signals is attracting increasing focus for describing mechanical behavior *** the statistical description of the spatial distribution of randomly generated AE signals,spatial correlation modeling is based mainly on short-range correlation considering the interrelationship of adjacent *** a new idea from percolation models,the covering strategy is used to build the most representative cube cluster,which corresponds to the critical scale at peak *** modeling process of critical cube cluster depends strongly on the full connection of the main fracture network,and the corresponding cube for coverage is termed the critical *** criticality pertains to not only the transition of local-to-whole connection of the fracture network but also the increasing-to-decreasing transition of the deviatoric stress with an obvious stress drop in the brittle failure of *** a reasonable critical cube guarantees the best observation scale for investigating the failure ***,the topological connection induces the geometric criticality of three descriptors,namely anisotropy,pore fraction,and specific surface area,which are evaluated separately and *** results show that cluster modeling based on the critical cube is effective and has criticality in both topology and geometry,as well as the triaxial ***,the critical cube length presents a high confidence probability of being correlated to the mineral particle ***,its pore fraction of cube cluster is influenced strongly by the critical cube length and confining pressure.

关键词： Acoustic emission Spatial correlation modeling Cover strategy Criticality Critical cube Cluster modeling

Coupling mechanism between mining-induced deformation and permeability of coal

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International Journal of Mining Science and Technology 2013年第6期23卷 783-787页

作者： xue dongjie Zhou Hongwei Wang Chaosheng Li Dongping School of Mechanics&Civil Engineering China University of Mining&Technology State Key Laboratory of Coal Resources and Safe Mining China University of Mining&Technology

The coupling mechanism between mining-induced mechanical behavior and gas permeability of coal is effectively obtained in *** study means significant understanding of the prevention of coal-gas *** testing samples of coal were drilled from the 14120 mining face at the depth of690 *** on the redistribution of stress during the excavation,the coupling test between mechanical state and seepage has been designed using the triaxial servo-controlled seepage equipment for thermofluid-solid coupling of coal containing *** is the result that there are two main factors influencing the mining-induced mechanical behavior of coal,such as the change ofσ_1-σ_3 andΔσ_1-Δσ_*** failure mode mainly depends on the value ofσ_1-σ_3,and the peak strength value mainly depends on the value ofΔσ_1-Δσ_*** difference of mechanical response between geostress and mining-induced stress has been obtained,which can be a theoretical support for safe mining such as reasonable gas drainage,prevention of coal-gas outburst and gas over-limit.

关键词： Mining-induced mechanical behavior Coal deformation Seepage Coupling test

Spatial correlation-based characterization of acoustic emission signal-cloud in a granite sample by a cube clustering approach

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International Journal of Mining Science and Technology 2021年第4期31卷 535-551页

作者： dongjie xue Zepeng Zhang Cheng Chen Jie Zhou Lan Lu Xiaotong Sun Yintong Liu School of Mechanics and Civil Engineering China University of Mining and Technology-BeijingBeijing 100083China State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing UniversityChongqing 400030China State Key Laboratory of Coal Resource and Safe Mining China University of Mining and Technology-BeijingBeijing 100083China

To extract more in-depth information of acoustic emission(AE)signal-cloud in rock failure under triaxial compression,the spatial correlation of scattering AE events in a granite sample is effectively described by the cube-cluster ***,the complete connection of the fracture network is regarded as a critical ***,according to the Hoshen-Kopelman(HK)algorithm,the real-time estimation of fracture con-nection is effectively made and a dichotomy between cube size and pore fraction is suggested to solve such a challenge of the one-to-one match between complete connection and cluster ***,the 3D cube clusters are decomposed into orthogonal layer clusters,which are then transformed into the ellip-soid ***,the anisotropy evolution of fracture network could be visualized by three orthogonal ellipsoids and quantitatively described by aspect ***,the other three quantities of centroid axis length,porosity,and fracture angle are analyzed to evaluate the evolution of cube *** result shows the sample dilatancy is strongly correlated to four quantities of aspect ratio,centroid axis length,and porosity as well as fracture ***,the cube cluster model shows a potential pos-sibility to predict the evolution of fracture ***,the cube cluster model provides an in-depth view of spatial correlation to describe the AE signal-cloud.

关键词： Acoustic emission Triaxial compression Fracture connection Spatial correlation Cube cluster model Dilatancy