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Verification of a laboratory-based dilation model for in situ conditions using continuum models 被引量:6
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作者 G.Walton M.S.Diederichs +1 位作者 L.R.Alejano J.Arzúa 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2014年第6期522-534,共13页
With respect to constitutive models for continuum modeling applications, the post-yield domain remainsthe area of greatest uncertainty. Recent studies based on laboratory testing have led to thedevelopment of a number... With respect to constitutive models for continuum modeling applications, the post-yield domain remainsthe area of greatest uncertainty. Recent studies based on laboratory testing have led to thedevelopment of a number of models for brittle rock dilation, which account for both the plastic shearstrain and confining stress dependencies of this phenomenon. Although these models are useful inproviding an improved understanding of how dilatancy evolves during a compression test, there hasbeen relatively little work performed examining their validity for modeling brittle rock yield in situ. Inthis study, different constitutive models for rock dilation are reviewed and then tested, in the context of anumber of case studies, using a continuum finite-difference approach (FLAC). The uncertainty associatedwith the modeling of brittle fracture localization is addressed, and the overall ability of mobilizeddilation models to replicate in situ deformation measurements and yield patterns is evaluated. 2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved. 展开更多
关键词 dilation Continuum models Case studies Brittle rock
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Considerations of rock dilation on modeling failure and deformation of hard rocks-a case study of the mine-by test tunnel in Canada 被引量:9
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作者 Xingguang Zhao Meifeng Cai MCai 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE 2010年第4期338-349,共12页
For the compressive stress-induced failure of tunnels at depth, rock fracturing process is often closely associated with the generation of surface parallel fractures in the initial stage, and shear failure is likely t... For the compressive stress-induced failure of tunnels at depth, rock fracturing process is often closely associated with the generation of surface parallel fractures in the initial stage, and shear failure is likely to occur in the final process during the formation of shear bands, breakouts or V-shaped notches close to the excavation boundaries. However, the perfectly elastoplastic, strain-softening and elasto-brittle-plastic models cannot reasonably describe the brittle failure of hard rock tunnels under high in-situ stress conditions. These approaches often underestimate the depth of failure and overestimate the lateral extent of failure near the excavation. Based on a practical case of the mine-by test tunnel at an underground research laboratory (URL) in Canada, the influence of rock mass dilation on the depth and extent of failure and deformation is investigated using a calibrated cohesion weakening and frictional strengthening (CWFS) model. It can be found that, when modeling brittle failure of rock masses, the calibrated CWFS model with a constant dilation angle can capture the depth and extent of stress-induced brittle failure in hard rocks at a low confinement if the stress path is correctly represented, as demonstrated by the failure shape observed in the tunnel. However, using a constant dilation angle cannot simulate the nonlinear deformation behavior near the excavation boundary accurately because the dependence of rock mass dilation on confinement and plastic shear strain is not considered. It is illustrated from the numerical simulations that the proposed plastic shear strain and confinement-dependent dilation angle model in combination with the calibrated CWFS model implemented in FLAC can reasonably reveal both rock mass failure and displacement distribution in vicinity of the excavation simultaneously. The simulation results are in good agreement with the field observations and displacement measurement data. 展开更多
关键词 hard rocks brittle failure deformation dilation angle model confinement plastic shear strain mine-by test tunnel
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A post-peak dilatancy model for soft rock and its application in deep tunnel excavation 被引量:7
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作者 Wuqiang Cai Hehua Zhu +3 位作者 Wenhao Liang Xiaojun Wang Chenlong Su Xiangyang Wei 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2023年第3期683-701,共19页
The dilation angle is the most commonly used parameter to study nonlinear post-peak dilatancy(PPD)behavior and simulate surrounding rock deformation;however,simplified or constant dilatancy models are often used in nu... The dilation angle is the most commonly used parameter to study nonlinear post-peak dilatancy(PPD)behavior and simulate surrounding rock deformation;however,simplified or constant dilatancy models are often used in numerical calculations owing to their simple mathematical forms.This study developed a PPD model for rocks(rock masses)based on the Alejanoe-Alonso(A-A)dilatancy model.The developed model comprehensively reflects the influences of confining pressure(σ_(3))and plastic shear strain(γ^(p)),with the advantages of a simple mathematical form,while requiring fewer parameters and demonstrating a clear physical significance.The overall fitting accuracy of the PPD model for 11 different rocks was found to be higher than that of the A-A model,particularly for Witwatersrand quartzite and jointed granite.The applicability and reliability of the PPD model to jointed granites and different scaled Moura coals were also investigated,and the model was found to be more suitable for the soft and large-scale rocks,e.g.deep rock mass.The PPD model was also successfully applied in studying the mechanical response of a circular tunnel excavated in strain-softening rock mass,and the developed semi-analytical solution was compared and verified with existing analytical solutions.The sensitivities of the rock dilatancy to γ^(p) and σ_(3) showed significant spatial variabilities along the radial direction of the surrounding rock,and the dilation angle did not exhibit a monotonical increasing or decreasing law from the elasticeplastic boundary to the tunnel wall,thereby presenting the σ3-or γ^(p)-dominated differential effects of rock dilatancy.Tunnel deformation parabolically or exponentially increased with increasing in situ stress(buried depth).The developed PPD model is promising to conduct refined numerical and analytical analyses for deep tunneling,which produces extensive plastic deformation and exhibits significant nonlinear post-peak behavior. 展开更多
关键词 Deep excavation Post-peak dilatancy(PPD)model AlejanoeAlonso(AeA)dilatancy model Soft rock
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Earthquake epicentroids in the Beijing- Tianjin-Tangshan-Zhangjiakou region inversed by gravity variation data 被引量:1
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作者 郑金涵 宋胜合 +2 位作者 刘克人 卢红艳 郭宗汾 《Acta Seismologica Sinica(English Edition)》 CSCD 2003年第4期449-458,共10页
Gravity variation data observed in the process of seismogenesis and occurrences of earthquakes show that the location with the greatest gravity changes does not necessarily coincide with the epicenter. To explain this... Gravity variation data observed in the process of seismogenesis and occurrences of earthquakes show that the location with the greatest gravity changes does not necessarily coincide with the epicenter. To explain this we defined the center of effective mass of stress volume as hypocentroid, and the vertical projection of which on the earths surface as epicentroid. Here we adopt three rotating models, including spheroid, ellipsoid and cylinder, to represent the region of an impending earthquake. Based on the models of gravity variations induced by uniform dilatancy, epicentroids associated with sixteen earthquakes with M>4.0 occurred in 1981~2000 in the Beijing-Tianjin-Tangshan-Zhangjiakou region are determined by means of a proposed least squares iterative inversion method. The results indicate that cylinder model is preferable to the other two, and epicentroids obtained by the cylinder model separate from the epicenters by a range of 0~40 km. Epicentroids are inevitably located within intact tectonic blocks, and usually cluster in groups; while the epicenters are generally located at the terminations of faults or at the intersections of faults. It seems that there exist earthquake-hatching areas in the block among faults. Earthquakes hatch in these areas, but occur around these areas, meanwhile the existence of faults may play an important role in controlling the processes. 展开更多
关键词 gravity variation dilatancy model epicentroid inversion +
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Shear strength criteria for rock,rock joints,rockfill and rock masses:Problems and some solutions 被引量:45
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作者 Nick Barton 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2013年第4期249-261,共13页
Although many intact rock types can be very strong,a critical confining pressure can eventually be reached in triaxial testing,such that the Mohr shear strength envelope becomes horizontal.This critical state has rece... Although many intact rock types can be very strong,a critical confining pressure can eventually be reached in triaxial testing,such that the Mohr shear strength envelope becomes horizontal.This critical state has recently been better defined,and correct curvature or correct deviation from linear Mohr-Coulomb(MC) has finally been found.Standard shear testing procedures for rock joints,using multiple testing of the same sample,in case of insufficient samples,can be shown to exaggerate apparent cohesion.Even rough joints do not have any cohesion,but instead have very high friction angles at low stress,due to strong dilation.Rock masses,implying problems of large-scale interaction with engineering structures,may have both cohesive and frictional strength components.However,it is not correct to add these,following linear M-C or nonlinear Hoek-Brown(H-B) standard routines.Cohesion is broken at small strain,while friction is mobilized at larger strain and remains to the end of the shear deformation.The criterion 'c then σn tan φ' should replace 'c plus σn tan φ' for improved fit to reality.Transformation of principal stresses to a shear plane seems to ignore mobilized dilation,and caused great experimental difficulties until understood.There seems to be plenty of room for continued research,so that errors of judgement of the last 50 years can be corrected. 展开更多
关键词 Rock masses Critical state Rock joints Shear strength Non-linear friction Cohesion dilation Scale effects Numerical modelling Stress transforms
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An engineering analysis of penetration of metal ball into fibre-reinforced composite targets
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作者 李永池 王志海 +2 位作者 王肖钧 胡秀章 Ren-huai LIU 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2009年第3期365-372,共8页
An engineering analysis of computing the penetration problem of a steel ball penetrating into fibre-reinforced composite targets is presented. Assume the metal ball is a rigid body, and the composite target is a trans... An engineering analysis of computing the penetration problem of a steel ball penetrating into fibre-reinforced composite targets is presented. Assume the metal ball is a rigid body, and the composite target is a transversely isotropic elasto-plastic material. In the analysis, a spherical cavity dilatation model is incorporated in the cylindrical cavity penetration method. Simulation results based on the modified model are in good agreement with the results for 3-D Kevlar woven (3DKW) composite anti-penetration experiments. Effects of the target material parameters and impact parameters on the penetration problem are also studied. 展开更多
关键词 fibre-reinforced composites engineering analysis transversely isotropic elasto-plastic materials spherical cavity dilatation model cylindrical cavity penetration model
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Model predictions for behaviors of sand-nonplastic-fines mixtures using equivalent-skeleton void-ratio state index 被引量:8
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作者 XIAO Yang SUN YiFei +3 位作者 LIU HanLong XIANG Jia MA QiFeng LONG LeiHang 《Science China(Technological Sciences)》 SCIE EI CAS CSCD 2017年第6期878-892,共15页
It is a challenge to suggest a constitutive model for describing the stress-strain behavior of sand-fines mixtures due to that these granular mixtures exhibited very complex behaviors at different densities, pressure... It is a challenge to suggest a constitutive model for describing the stress-strain behavior of sand-fines mixtures due to that these granular mixtures exhibited very complex behaviors at different densities, pressures and fines contents. In this study, an elastoplastic constitutive model within the framework of the bounding surface plasticity and critical state theories was proposed for sand-nonplastic-fines mixtures by using the concept of the equivalent-skeleton void ratio and equivalent-skeleton void-ratio state index. The proposed model with a set of material constants calibrated from a few tests could be used to model the fines-dependent and state-dependent behaviors of the sand-nonplastic-fines mixture including the strain- softening and volumetric-expansion behaviors in the drained triaxial compression tests, and also the effects of fines content on the critical state lines in both the deviatoric stress versus mean effective stress and the void ratio versus mean effective stress planes. 展开更多
关键词 sand fines equivalent-skeleton void ratio critical-state strength dilatancy constitutive model
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