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Experimental study on failure characteristics of single-sided unloading rock under different Intermediate principal stress conditions

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International Journal of Mining Science and Technology 2023年第3期33卷 275-287页

作者： Chongyan Liu Guangming Zhao Wensong Xu Xiangrui Meng Zhixi Liu Xiang Cheng Gang Lin State Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines Anhui University of Science and TechnologyHuainan 232001China Key Laboratory of Safe and Effective Coal Mining Ministry of EducationAnhui University of Science and TechnologyHuainan 232001China Post-Doctoral Research Station Huaibei Mining Corporation LimitedHuaibei 235006China Laboratoire de Géologie Ecole Normale SupérieureParis 75005France

Investigation of unloading rock failure under differentσ_(2)facilitates the control mechanism of excavation surrounding rock.This study focused on single-sided unloading tests of granite specimens under true triaxial conditions.The strength and failure characteristics were studied with micro-camera and acoustic emission(AE)monitoring.Furthermore,the choice of test path and the effect ofσ_(2)on fracture of unloading rock were discussed.Results show that the increasedσ_(2)can strengthen the stability of single-sided unloading rock.After unloading,the rock’s free surface underwent five phases,namely,inoculation,particle ejection,buckling rupture,stable failure,and unstable rockburst phases.Moreover,atσ_(2)≤30 MPa,the b value shows the following variation tendency:rising,dropping,significant fluctuation,and dropping,with dispersed damages signal.Atσ_(2)≥40 MPa,the tendency shows:a rise,a decrease,a slight fluctuation,and final drop,with concentrated damages signal.After unloading,AE energy is mainly concentrated in the micro-energy range.With the increasedσ_(2),the micro-energy ratio rises.In contrast,low,medium and large energy ratios drop gradually.The increased tensile fractures and decreased shear fractures indicate that the failure mode of the unloading rock gradually changes from tensile-shear mode to tensile-split one.The fractional dimension of the rock fragments first increases and then decreases with an inflection point at 20 MPa.The distribution of SIF on the planes changes asσ_(2)increases,resulting in strengthening and then weakening of the rock bearing capacity.

关键词： Single-sided unloading Acoustic emission True triaxial Intermediate principal stress stress intensity factor

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Failure criterion for soft rocks considering Intermediate principal stress

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International Journal of Mining Science and Technology 2021年第4期31卷 565-575页

作者： Zhongwei Wang Quansheng Liu Key Laboratory of Safety for Geotechnical and Structural Engineering of Hubei Province School of Civil EngineeringWuhan UniversityWuhan 430072China State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan UniversityWuhan 430072China

The significant differences between hard rocks(more brittle)and soft rocks(more ductile)may suggest the use of different failure criteria.A strength criterion for soft rocks that includes Intermediate principal stress was proposed.The new criterion includes two independent parameters:the uniaxial compressive strength(σ_(ci)),which can be obtained from common laboratory tests or indirectly estimated by alternative index tests in the laboratory or field;and f(joint),which is used to characterize the rock mass quality and can be easily estimated.The authors compared the predictive capabilities of the new criterion with other criteria using the database of soft rocks under two conditions:with and without triaxial data.For the estimation of triaxial and true-triaxial strengths,the new criterion generally produced a better fit.The proposed criterion is practical for an approximate first estimation of rock mass strength,even without triaxial data,as it balances accuracy(lower prediction error)and simplicity(fewer independent parameters).

关键词： Soft rock Intermediate principal stress Failure criterion True-triaxial Uniaxial compressive strength

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Investigation of the influence of Intermediate principal stress on the dynamic responses of rocks subjected to true triaxial stress state

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International Journal of Mining Science and Technology 2021年第5期31卷 913-926页

作者： Wei You Feng Dai Yi Liu Hongbo Du Ruochen Jiang State Key Laboratory of Hydraulics and Mountain River Engineering College of Water Resource and HydropowerSichuan UniversityChengdu 610065China

Precisely understanding the dynamic mechanical properties and failure modes of rocks subjected to true triaxial stress state(σ1>σ2>σ3,whereσ1,σ2,andσ3 are the major principal stress,Intermediate principal stress,and minor principal stress,respectively)is essential to the safety of underground engineering.However,in the laboratory,it is difficult to maintain the constant true triaxial stress state of rocks during the dynamic testing process.Herein,a numerical servo triaxial Hopkinson bar(NSTHB)was developed to study the dynamic responses of rocks confronted with a true triaxial stress state,in which lateral stresses can maintain constant.The results indicate that the dynamic strength and elastic modulus of rocks increase with the rise of Intermediate principal stressσ2,while the dynamic elastic modulus is independent of the dynamic strain rate.Simulated acoustic emission distributions indicate that the Intermediate principal stressσ2 dramatically affects dynamic failure modes of triaxial confined rocks.Asσ2 increases,the failure pattern switches from a single diagonal shear zone into two parallel shear zones with a small slant.Moreover,a recent triaxial Hopkinson bar experimental system using three bar pairs is also numerically established,and the measuring discrepancies are identified between the two numerical bar systems.The proposed NSTHB system provides a controllable tool for studying the dynamic triaxial behavior of rocks.

关键词： Triaxial Hopkinson bar Intermediate principal stress Dynamic strength Failure modes Numerical simulation True triaxial stress

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Estimation of the Passive Earth Pressure with Inclined Cohesive Backfills:the Effect of Intermediate principal stress is Considered

Estimation of the Passive Earth Pressure with Inclined Cohes...

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中国科学院地质与地球物理研究所第11届（2011年度）...

作者： W.L.Yu~(*,1,2),J.Zhang~1,R.L.Hu~1,Z.Q.Li~1,X.H.Sun~2,R.X.Wang~3 and Y.Q.Wang~4 1 Key Laboratory of Engineering Geomechanics,Institute of Geology and Geophysics,Chinese Academy of Sciences, Beijing 100029,China 2 Exploration and Development Research Institute,Daqing Oil Field Company Ltd.,Daqing,Heilongjiang 163712, China 3 Beijing Orangelamp Navigation Technology Development Co.,Ltd,Beijing 10085,China 4 Henan Provincial Communications Planning Survey and Design Institute Co.,Ltd.Zhenzhou 450052,China

Estimating passive earth pressure accurately is very important when designing retaining wall.Based on the unified strength theory and plane strain assumption,an analytical solution has been developed to determine the passive lateral earth pressure distribution on a retaining structure when the backfill is cohesive and inclined considering the effect of the Intermediate principal stress.The solution derived encompasses both Bell’s equation(for cohesive or cohesionless backfill with a horizontal ground surface) and Rankine’s solution(for cohesionless backfill with an inclined ground surface).

关键词： Passive earth pressure inclined backfill unified strength theory Intermediate principal stress

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Estimation of the Active Earth Pressure with Inclined Cohesive Backfills:the Effect of Intermediate principal stress is Considered

Estimation of the Active Earth Pressure with Inclined Cohesi...

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中国科学院地质与地球物理研究所第11届（2011年度）...

作者： W.L.Yu~(1,2,*),J.Zhang~1,R.L.Hu~1,Z.Q.Li~1,X.H.Sun~2 and T.L.Li~3 1 Key Laboratory of Engineering Geomechanics,Institute of Geology and Geophysics,Chinese Academy of Sciences, Beijing 100029,China 2 Exploration and Development Research Institute,Daqing Oil Field Company Ltd.,Daqing,Heilongjiang 163712,China 3 China Building Technique Group Co.,Ltd,Beijing 100029,China

Estimating active earth pressure accurately is very important when designing retaining wall.Based on the unified strength theory and plane strain assumption,an analytical solution has been developed to determine the active lateral earth pressure distribution on a retaining structure with the inclined cohesive backfill considering the effect of the Intermediate principal stress.The solution derived encompasses both Bell’s equation(for cohesive or cohesionless backfill with a horizontal ground surface) and Rankine’s solution(for cohesionless backfill with an inclined ground surface).

关键词： Active earth pressure inclined cohesive backfill Intermediate principal stress Rankine’s theory Bell’s equation

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Estimation of the Passive Earth Pressure with Inclined Cohesive Backfills:the Effect of Intermediate principal stress is Considered

Estimation of the Passive Earth Pressure with Inclined Cohes...

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中国科学院地质与地球物理研究所第11届（2011年度）...

作者： Wenlong Yu~(1,a),Jian Zhang~(1,b),Xiuhua Sun~(2,c),Ruilin Hu~(1,d) and Xin Wei~(1,e) 1 Key Laboratory of Engineering Geomechanics,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China 2 Exploration and Development Research Institute,Daqing Oil Field Company Ltd.,Daqing, Heilongjiang 163712,China

关键词： passive earth pressure inclined backfill unified strength theory Intermediate principal stress

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EFFECTS OF Intermediate principal stress ON COMPRESSIVE AND TENSILE STRENGTHS OF SANDSTONES

EFFECTS OF INTERMEDIATE PRINCIPAL STRESS ON COMPRESSIVE AND ...

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2009 International Symposium on Rock Mechanics:"Rock Characterisation,Modelling and Engineering Design Methods"

作者： R.Thosuwan C.Walsri P.Poonprakon K.Fuenkajorn Suranaree University of Technology Nakorn Ratchasima

A series of true triaxial compression tests and indirect tension tests with axial confinements are performed to assess the effects of the Intermediate principal stresses on the elasticity and stren

ISBN: (纸本)9789628014170

A series of true triaxial compression tests and indirect tension tests with axial confinements are performed to assess the effects of the Intermediate principal stresses on the elasticity and stren

关键词： failure envelope extension tests sandstone Intermediate principal stress MULTIAXIAL Compression tests Tensile Strength failure criteria

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Analytical solutions for deep tunnels in strain-softening rocks modeled by different elastic strain definitions with the unified strength theory

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Science China(Technological Sciences) 2022年第10期65卷 2503-2519页

作者： SUN ZhenYu ZHANG DingLi FANG Qian DUI GuanSuo CHU ZhaoFei Key Laboratory for Urban Underground Engineering of Ministry of Education Beijing Jiaotong UniversityBeijing 100044China School of Civil Engineering Wuhan UniversityWuhan 430072China

This paper presents the analytical solutions for the responses of tunnels excavated in rock masses exhibiting strain-softening behavior. Since previous analyses give little consideration to the effect of the Intermediate principal stress on the strain-softening rock behavior, the unified strength theory was introduced to analyze the tunnel response. Four cases of different definitions of the elastic strain in the softening and residual regions, used in the existing solutions, were considered. The tunnel displacements,stresses, radii of the softening and residual zones and critical stresses were deduced. The proposed solutions were verified by comparing with numerical simulations, model tests and existing solutions. Furthermore, the solutions of the four cases were compared with each other to investigate the influence of the elastic strain expressions on the tunnel responses. The results showed that the Intermediate principal stress coefficient b has a significant effect on the tunnel displacements, stress fields, and plastic radii. Parametric studies were performed to analyze the influences of the softening and residual dilatancy coefficients,softening modulus and residual strength on the tunnel responses. The parametric analysis indicated that the existing models should be carefully evaluated in the analysis of tunnels constructed through average-quality rocks;the proposed solutions outperformed the existing models in solving the mentioned problem.

关键词： analytical solution elastic strain definition unified strength theory strain-softening Intermediate principal stress model test

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Comparative analysis of deformation and failure mechanisms of underground powerhouses on the left and right banks of Baihetan hydropower station

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第3期14卷 731-745页

作者： Anchi Shi Congjiang Li Wangbing Hong Gongda Lu Jiawen Zhou Haibo Li PowerChina Huadong Engineering Corporation Limited HangzhouChina State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan UniversityChengdu610065China College of Water Resource and Hydropower Sichuan UniversityChengdu610065China

The stability of the surrounding rocks of large underground powerhouses is always emphasized during the construction process,especially in large-scale underground projects under construction,such as the Baihetan hydropower station in China.According to field investigations,numerical simulations and monitoring data analysis,we present a comparative analysis of the deformation and failure characteristics of the surrounding rocks of underground powerhouses on the left and right banks of the Baihetan hydropower station.The failure characteristics and deformation magnitude of the underground powerhouses on the left and right banks are quite different.Under the disadvantageous condition where the maximum principal stress intersects the axis of the powerhouse at a large angle,the left bank underground powerhouse shows prominent stress-controlled failure characteristics such as spalling,slack collapse and concrete cracking.Although the maximum principal stress is in the favorable condition which intersects the right bank powerhouse at a small angle,the relatively high Intermediate principal stress with an angle subvertical to the right bank powerhouse plays an essential role in its deformation and failure,indicating that the influence of high Intermediate principal stress cannot be ignored.In addition,structural plane-controlled failure and large deformation are also more evident on the right bank due to the extensive distribution of weak structural planes and complex surrounding rock properties.

关键词： Underground powerhouse stress-controlled failure Structural plane-controlled failure Large deformation Intermediate principal stress

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Three-dimensional DEM investigation of the stress-dilatancy relation of grain-cementing type methane hydrate-bearing sediment

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Petroleum 2021年第4期7卷 477-484页

作者： An Zhang Mingjing Jiang Wenhao Du School of Civil Engineering Suzhou University of Science and TechnologySuzhouJiangsu215009China Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering Ocean University of ChinaQingdao266000China State Key Laboratory for Disaster Reduction in Civil Engineering Tongji University Shanghai200092China Department of Geotechnical Engineering College of Civil EngineeringTongji UniversityShanghai200092China Department of Civil Engineering Tianjin UniversityTianjin300072China Tongji Architectural Design(Group)Co. Ltd.No.1230 Siping RoadShanghai200092China

In this study,the Discrete Element Method(DEM)was employed to investigate numerically the effects of hydrate cementation and Intermediate principal stress on the stress-dilatancy relation of graincementing type methane hydrate-bearing sediment(MHBS)by conducting a series of conventional and true triaxial tests.A novel 3D thermo-hydro-mechanical-chemical(THMC)contact model for MHBS was employed.The numerical results show that with increasing hydrate saturation and back pressure,or decreasing confining pressure,temperature and salinity,the stress-dilation relation of grain-cementing type MHBS evolves from dilation-dominant to bond-dominant.For the clean sand samples,the relationship between the normalized stress ratio h/Mcr and the dilatancy rate d is close under different intermediate principal stress coefficients.However,for the MHBS samples,this relationship is still affected by the Intermediate principal stress coefficient b,due to the effect of hydrate cementation.

关键词： stress-dilatancy Cementation Methane hydrate bearing sediment Discrete element method Intermediate principal stress

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