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An improved strain-softening constitutive model of granite considering the effect of crack deformation

Journal of Rock mechanics and geotechnical engineering 2024年第4期16卷 1202-1215页

作者： Yapeng Li Qiang Zhang Qiuxin Gu Peinan Wu Binsong Jiang State Key Laboratory for Geomechanics and Deep Underground Engineering School of Mechanics and Civil EngineeringChina University of Mining and TechnologyXuzhou221116China

This paper presents an improved strain-softening constitutive model considering the effect of crack deformation based on the triaxial cyclic loading and unloading test *** improved model assumes that total strain is a combination of plastic,elastic,and crack *** constitutive relationship between the crack strain and the stress was further *** evolutions of mechanical parameters,*** parameters,dilation angle,unloading elastic modulus,and deformation parameters of crack,with the plastic strain and confining pressure were *** the increase in plastic strain,the cohesion,friction angle,dilation angle,and crack Poisson's ratio initially increase and subsequently decrease,and the unloading elastic modulus and the crack elastic modulus nonlinearly *** increasing confining pressure enhances the strength and unloading elastic modulus,and decreases the dilation angle and Poisson's ratio of the *** theoretical triaxial compressive stress-strain curves were compared with the experimental results,and they present a good agreement with each *** improved constitutive model can well reflect the nonlinear mechanical behavior of granite.

关键词： Strain-softening Crack deformation effect Plastic shear strain Constitutive model

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Numerical simulation study on particle breakage behavior of granular materials in confined compression tests

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Particuology 2023年第3期74卷 18-34页

作者： Yang Yu Guangsi Zhao Minghui Ren State Key Laboratory for Geomechanics and Deep Underground Engineering School of Mechanics and Civil EngineeringChina University of Mining and TechnologyXuzhou221116China

In order to study the fragmentation law,the confined compression experiment of granular assemblies has been conducted to explore the particle breakage characteristic by DEM approach in this *** is shown that contact and contact force during the loading process gradually transform from anisotropy to ***,two particle failure modes caused by different contact force states are analyzed,which are single-through-crack failure and multi-short-crack *** the vertical distribution of the number of cracks and the four characteristic stress distributions(the stress related to the maximum contact force,the major principal stress,the deviatoric stress and the mean stress),it is pointed out that the stress based on the maximum contact force and the major principal stress can reflect the distribution of cracks *** addition,the size effect of particle crushing indicates that small size particles are prone to *** lateral pressure coefficient of four size particles during the loading process is analyzed to explain the reason for the size effect of particle breakage.

关键词： Granular materials Confined compression Particle breakage Meso-mechanics Discrete element method

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Rock dynamics in deep mining

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International Journal of Mining Science and Technology 2023年第9期33卷 1065-1082页

作者： Manchao He Qi Wang State Key Laboratory for Geo-mechanics and Deep Underground Engineering China University of Mining&Technology-BeijingBeijing 100083China

Rock mass dynamics disasters caused by excavations and mining occur frequently in deep *** order to establish a theoretical system and control technologies for such disasters,we first classify and define dynamic disasters,such as rock bursts,coal bursts,mine pressure bumps,and mine *** to the occurrence mechanism of different types of dynamic disasters,we establish a compensation control theory based on excavation and mining *** the basis,we propose three key technologies:high prestress compensation technology for the roadway,pressure relief technology using directional roof cutting,and the goaf filling technology using broken rock *** three technologies constitute the compensation control method for dynamic disasters in deep ***,this method was successfully applied in a deep coal mine with high stress,with monitored results suggesting its *** work provides a new concept and control method for the prevention of rock dynamic disasters in deep mines.

关键词： Rock burst Coal burst Mine pressure bump Mine earthquake Excavation compensation control Mining compensation control

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Impact of cooling rate on mechanical properties and failure mechanism of sandstone under thermal-mechanical coupling effect

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International Journal of Coal Science & Technology 2023年第2期10卷 97-116页

作者： Pingye Guo Peng Zhang Mohua Bu Hang Xing Manchao He State Key Laboratory for Geo-Mechanics and Deep Underground Engineering Beijing 100083China School of Mechanics and Civil Engineering China University of Mining and TechnologyBeijing 100083China

High geo-temperature is one of the inevitable geological disasters in deep engineering such as resource extraction,space development,and energy *** of the key issues is to understand the mechanical properties and failure mechanism of high-temperature rock disturbed by low-temperature airflow after ***,.the experimental and numerical investigation were carried out to study the impact of cooling rate on mechanical properties and failure mechanism of high temperature ***,uniaxial compression experiments of high temperature sandstone at different real-time cooling rates were carried out to study the mechanical properties and failure *** experimental results indicate that the cooling rate has a significant effect on the mechanical properties and failure modes of *** peak strain,peak stress,and elastic modulus decrease with an increase in cooling rate,and the fragmentation degree after failure increases ***,the equivalent numerical model of heterogeneous sandstone was established using particle flow code(PFC)to reveal the failure *** results indicate that the sandstone is dominated by intragrain failure in the cooling stage,the number of microcracks is exponentially related to the cooling rate,and the higher the cooling rate,the more cracks are concentrated in the exterior *** axial loading,the tensile stress is mostly distributed along the radial direction,and the damage in the cooling stage is mostly due to the fracture of the radial *** addition,axial loading,temperature gradient and thermal stress mismatch between adjacent minerals are the main reasons for the damage of sandstone in the cooling ***,the excessive temperature gradient in the exterior region of the sandstone is the main reason for the damage concentration in this region.

关键词： High geo-temperature Thermo-mechanical coupling effect Cooling rate Sandstone PFC

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An improved elastoplastic model for rocks and application to cyclic loading and unloading triaxial compression tests

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Acta Mechanica Sinica 2024年第8期40卷 179-193页

作者： Qiuxin Gu Qiang Zhang Yapeng Li Peinan Wu Guilei Han State Key Laboratory for Geomechanics and Deep Underground Engineering School of Mechanics and Civil EngineeringChina University of Mining and TechnologyXuzhou221116China North China Engineering Investigation Institute Shijiazhuang050021China

The recoverable strain of rock is completely classified as elastic strain in the conventional elastic-plastic theory,which often results in poor agreement between theoretical and experimental *** work proposes an improved elastoplastic model of rock materials considering the evolutions of crack deformation and elastic modulus to better characterize the nonlinear mechanical behavior of rock in the post-peak *** this model,the recoverable strain is assumed to be a combination of elastic and crack strain,and the constitutive relationship between crack strain and rock stress is *** on the proposed assumption,the evolutions of the mechanical parameters including strength parameters,elastic,plastic,and crack deformation parameters versus the plastic strain and confining stress were *** developed elastoplastic model was validated by comparing the theoretical values with the results of the triaxial cyclic loading and unloading *** theoretical calculation results show a good agreement with the laboratory test,which indicates that the improved elastoplastic model can effectively reflect the nonlinear mechanical behavior of the rock *** research results are expected to provide a valuable reference for further understanding the evolution of rock crack deformation.

关键词： Crack strain Elastic modulus deterioration Novel elastoplastic model Model validation

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A consecutive joint shear strength model considering the 3D roughness of real contact joint surface

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International Journal of Mining Science and Technology 2023年第5期33卷 617-624页

作者： Liren Ban Zhigang Tao Weisheng Du Yuhang Hou School of Civil and Transportation Engineering Beijing University of Civil Engineering and ArchitectureBeijing 100044China State Key Laboratory of Deep Geotechnical Mechanics and Deep Underground Engineering Beijing 100083China State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan 430071China School of Mechanics and Civil Engineering China University of Mining and TechnologyBeijing 100083China Deep Mining and Rock Burst Research Branch China Coal Research InstituteBeijing 100013China State Key Laboratory of Hydroscience and Engineering Tsinghua UniversityBeijing 100084China

A consecutive joint shear strength model for soft rock joints is proposed in this paper,which takes into account the degradation law of the actual contact three-dimensional(3D)*** essence of the degradation of the maximum possible dilation angle is the degradation of the 3D average equivalent dip angle of the actual contact joint ***,models for calculating the maximum possible dilation angle at the initial and residual shear stress stages are proposed by analyzing the 3D joint morphology characteristics of the corresponding shear ***,the variation law of the maximum possible dilation angle is quantified by studying the degradation law of the joint micro convex *** on the variation law of the maximum possible dilation angle,the maximum possible shear strength model is ***,a method to calculate the shear stiffness degradation in the plastic stage is *** to the maximum possible shear strength of rock joints,the shear stress-shear displacement prediction model of rock joints is *** new model reveals that there is a close relationship between joint shear strength and actual contact joint roughness,and the degradation of shear strength after the peak is due to the degradation of actual contact joint roughness.

关键词： Shear strength Actual contact area 3D roughness Shear test

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Anisotropic fracture behavior and corresponding fracture process zone of laminated shale through three-point bending tests

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Journal of Rock mechanics and geotechnical engineering 2025年第2期17卷 757-774页

作者： Peng Chu Heping Xie Jianjun Hu Minghui Li Li Ren Cunbao Li State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering Institute of Deep Earth Sciences and Green EnergyShenzhen UniversityShenzhen518060China Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization College of Civil and Transportation EngineeringShenzhen UniversityShenzhen518060China Shenzhen Key Laboratory of Deep Underground Engineering Sciences and Green Energy Shenzhen UniversityShenzhen518060China MOE Key Laboratory of Deep Earth Science and Engineering Sichuan UniversityChengdu610065China

Understanding the anisotropic fracture behavior and the characteristics of the fracture process zone(FPZ)under size effects in laminated rocks,as well as its role in rock fracturing,is crucial for various engineering *** this study,three-point bending tests were conducted on shale specimens with varying bedding angles and *** anisotropic characteristics and size effects of fracture parameters were revealed.A comparative analysis was performed on the evolutions of FPZs computed using size effect theory,digital image correlation(DIC),and linear elastic fracture *** results divulged that:(i)With increasing bedding angles,there is a noticeable decrease in apparent fracture toughness(KICA),apparent fracture energy(GICA),and nominal strength(σ_(Nu)).When the bedding angle of shale is less than 45°,the crack propagation and fracture parameters are mainly influenced by the ***,shale with bedding angles greater than 60°,the crack propagation and fracture parameters are mainly controlled by the *** the bedding angle is between 45°and 60°,the fracture propagation evolves from permeating the matrix to extending along the bedding;(ii)The fracture parameters exhibit significant size dependent behavior,as KICA and GICA rise with increasing specimen size,butσNu falls with increasing specimen *** fracture parameters align with the theoretical predictions of Bažant size effect law;and(iii)The lengths of DIC-based FPZ,effective FPZ,and inelastic zone follow W-shape variations with bedding *** dimensionless sizes of FPZ and inelastic zone decrease with specimen size,indicating a size ***,there is a negative relation between KICA and the dimensionless size of the FPZ,whileσNu is positively correlated to the dimensionless size of the *** highlights the essential role of the FPZ in the size effect of rock *** bedding angle exerts an influence on the FPZ,subsequently affecting the anisotropic fracture

关键词： Anisotropic Size effect Fracture process zone Fracture toughness Fracture energy

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Negative Poisson’s ratio cable compensation support for 32 m super-large-span highway tunnel:A case study

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underground Space 2024年第1期14卷 156-175页

作者： Aipeng Guo Manchao He Songyuan Liu Zhifeng Du Zengwang Lyu Zhigang Tao State Key Laboratory for Geomechanics and Deep Underground Engineering Beijing 100083China School of Mechanics and Civil Engineering China University of Mining and Technology(Beijing)Beijing 100083China Department of Civil and Mineral Engineering University of TorontoToronto M5S 1A4Canada State Key Laboratory for Geomechanics and Deep Underground Engineering Sanmenxia Research CenterHenan 472099China

Although super-large-span tunnels ensure convenient transportation,they face many support *** lack of normative construction guidance and the limited number of reference engineering cases pose a significant challenge to the stability control of superlarge-span *** on the geological conditions of a super-large-span tunnel(span=32.17 m)at the bifurcation section of the Shenzhen interchange,this study determined support parameters via theoretical calculation,numerical simulation,and engineering *** support effects of negative Poisson’s ratio(NPR)anchor cables and ordinary anchor cables on super-long-span tunnels were simulated and ***,based on FLAC3D simulations,the surrounding rock stress field of NPR anchor cables was analyzed under different prestressing conditions,and the mechanism of a long-short combination,high-prestress compensation NPR anchor cable support was *** the basis of numerical simulations,to our knowledge,the three-dimensional(3D)geomechanical model test of the NPR anchor cable and ordinary anchor cable support for super-large-span tunnel excavation is conducted for the first time,revealing the stress evolution law of super-large-span tunnels,deformation and failure characteristics of the surrounding rock,and the changing trend of the anchor cable’s axial force,and verifies that NPR anchor cables with high preloads are suitable for super-large-span tunnel support and have advantages over ordinary anchor *** study can provide a reliable theoretical reference for the support design and stability control of the surrounding rock of similar shallow-buried super-large-span tunnels.

关键词： Super-large-span tunnel Negative Poisson’s ratio(NPR)anchor cable Excavation compensation method Numerical simulation Geomechanical model test

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Fracture behavior of sandstone with partial filling flaw under mixed-mode loading: Three-point bending tests and discrete element method

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Journal of Rock mechanics and geotechnical engineering 2025年第1期17卷 291-308页

作者： Dongdong Ma Yu Wu Xiao Ma Xunjian Hu Wenbao Dong Decheng Li Lingyu Li State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhou221116China State Key Laboratory of Structural Health and Safety of Bridges Wuhan430034China Research Center of Coastal and Urban Geotechnical Engineering Zhejiang UniversityHangzhou310058China State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China

The fracture behavior of natural fracture in the geological reservoir subjected to filling property,affects the crack initiation and propagation under stress *** filling flaws were intermediate between open fractures and filled fractures,the fracture response may be worth *** this work,the effect of the filling property of sandstone with partial filling flaws on the fracture behavior was systematically investigated based on three-point bending tests and the numerical approach of discrete element method(DEM).In the laboratory,semi-circular three-point bending tests were carried out with partial filling flaws of various filling *** on this,numerical simulations were used to further investigate the effect of the filling ratio and the inclination of the partial filling flaw on the mechanical and fracture responses,and the effect of the partial filling flaw under mixed-mode loading on the fracture mechanism was elucidated coupled with acoustic emission(AE)*** obtained results showed that the increase in filling strength and filling ratio of partial filling flaw led to an increase in peak strength,with a decreasing trend in peak strength with the inclination of partial filling *** terms of crack propagation pattern,the increasing filling strength of the partial filling flaw induced the transformation of the fracture mechanism toward deflection,with a tortuosity path,while the filling ratio and inclination of partial filling flaw led to fracture mechanism change from deflection to penetration and attraction,accompanied with a larger AE event source in ***,the b-value based on the Gutenberg-Richter equation fluctuated between 5 and 4 at low filling ratio and inclination and remained around 5 at high filling ratio and inclination of partial filling *** results may provide an application prospective for reservoir stimulation using the natural fracture system.

关键词： Partial filling flaw Mixed-mode loading Semi-circular three-point bending Acoustic emission(AE) b-value

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Numerical simulation study on shear resistance of anchorage joints considering tensile-shear fracture criterion of 2G-NPR bolt

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International Journal of Coal Science & Technology 2023年第4期10卷 186-202页

作者： Shulin Ren Zhigang Tao Manchao He Mengnan Li Qiru Sui State Key Laboratory for Geomechanics and Deep Underground Engineering Beijing 100083China School of Mechanics and Civil Engineering China University of Mining and TechnologyBeijing 100083China

2G-NPR bolt (the 2nd generation Negative Poisson’s Ratio bolt) is a new type of bolt with high strength, high toughness and no yield platform. It has signifcant efects on improving the shear strength of jointed rock mass and controlling the stability of surrounding rock. To achieve an accurate simulation of bolted joint shear tests, we have studied a numerical simulation method that takes into account the 2G-NPR bolt's tensile–shear fracture criterion. Firstly, the indoor experimental study on the tensile–shear mechanical properties of 2G-NPR bolt is carried out to explore its mechanical properties under diferent tensile–shear angles, and the fracture criterion of 2G-NPR bolt considering the tensile–shear angle is established. Then, a three-dimensional numerical simulation method considering the tensile–shear mechanical constitutive and fracture criterion of 2G-NPR bolt, the elastoplastic mechanical behavior of surrounding rock and the damage and deterioration of grouting body is proposed. The feasibility and accuracy of the method are verifed by comparing with the indoor shear test results of 2G-NPR bolt anchorage joints. Finally, based on the numerical simulation results, the deformation and stress of the bolt, the distribution of the plastic zone of the rock mass, the stress distribution and the damage of the grouting body are analyzed in detail. The research results can provide a good reference value for the practical engineering application and shear mechanical performance analysis of 2G-NPR bolt.

关键词： Anchorage joints 2G-NPR bolt Tensile-shear fracture criterion Shear behavior Numerical simulation

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