围压对锦屏深埋大理岩力学特性影响研究

Study on the Mechanical Behavior of Jinping Deep Marble Considering the Confining Pressure Effect

岩石力学特性是正确评价工程岩体稳定性的基础.通过三轴压缩试验,研究了围压对锦屏深埋大理岩弹性模量、泊松比、临界破裂条件和剪胀角的影响规律,提出了弹塑脆性力学模型.结果表明:(1)大理岩弹性模量和泊松比均随围压呈指数增大规律,而剪胀角随围压增大呈指数减小规律;(2)岩石强度达到弹性极限后表现出近似理想塑性承载特性,当其塑性剪应变达到临界条件时产生脆性破坏,且临界塑性剪应变亦随围岩呈指数增大;(3)基于Mohr-Coulomb(M-C)强度准则的峰值强度和残余强度随围压增大而增大,当围压为73.95MPa时两者理论上相等,符合锦屏深埋大理岩脆-延转换特性.基于大理岩弹性和强度参数演变规律的全应力-应变曲线与三轴试验结果具有良好的一致性,可为类似工程岩体稳定性分析和支护结构优化设计提供依据.

The mechanical behavior is the foundation of correctly evaluating the stability for rock mass.Based on the triaxial compression tests,the influence of confining pressure on the elastic modulus,Poisson’s ratio,critical failure condition and dilation angle was analyzed.The results show that:(1)the elastic modulus and Poisson’s ratio of marble manifest an exponential increasing law as confining pressure,while dilation angle decreases exponentially as confining pressure;(2)the marble manifests an ideal plastic bearing characteristic after the stress reaching the limit of elasticity,and brittle failure immediately occurs once the plastic shear strain,which also shows an exponential increasing with confining pressure,reaches the critical value;(3)both of the peak and residual strength for the Mohr-Coulomb(M-C)strength criterion increase with confining pressure,and the peak and residual strength theoretically equal to each other when confining pressure is 73.95 MPa.This is conformed to the brittle-ductile transition character of Jinping deep marble.The theoretical complete stress-strain curves based on the obtained evolution laws of elastic and strength parameters are in consistent with test results.Moreover,the results can provide a reference for stability evaluation and structure optimization of similar engineering.