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不同围压下岩石应变软化与剪胀特性不同,若在隧洞开挖中考虑围岩塑性区域内变化围压影响,其应力–应变场求解方式将区别于既有文献中的传统方法。根据围压影响下应变软化围岩的临界塑性剪切应变变化特征,给出改进的判断围岩是否进入塑性残余区域的规则;引入考虑围压与临界塑性剪切应变的非线性剪胀模型。基于Hoek-Brown屈服准则,根据一定径向应力增量将围岩塑性软化与残余区域分层,采用有限差分法对围岩应力–应变场进行求解;为分析围压对围岩稳定性的影响,根据临界塑性剪切应变与剪胀系数变化与否,设定4种非线性力学模型,深入分析并比较4种力学模型下临界塑性剪切应变、剪胀系数与围岩变形等在塑性软化与残余区域的分布规律。研究结果表明:地质强度指标GSI较小时,考虑围压影响下的围岩应力–应变场与未考虑时差异明显;此时临界塑性剪切应变的减小对开挖边界的围岩剪胀性具一定抑制作用。
Under different confining pressures, the strain softening and dilatancy characteristics of rock are different. If considering the influence of confining pressures in the plastic zone of surrounding rock under tunnel excavation, the solution of stress-strain field will be different from the traditional methods in the existing literature. According to the characteristics of the critical plastic shear strain of surrounding rock under strain confinement, an improved rule to judge whether the surrounding rock enters the plastic residual region is given. A nonlinear dilatancy model considering the confining pressure and the critical plastic shear strain is introduced. Based on the Hoek-Brown yield criterion, the plastic softening and stratification of surrounding rock are stratified according to a certain increment of radial stress. The finite difference method is used to solve the stress-strain field of surrounding rock. In order to analyze the influence of confining pressure on the stability of surrounding rock, According to the change of critical plastic shear strain and dilatancy coefficient, four kinds of nonlinear mechanical models are set up to analyze and compare the critical plastic shear strains, the dilatancy coefficients and the deformation of surrounding rock under plastic deformation And the distribution of the residual area. The results show that when the GSI of geological strength is small, the difference of stress-strain field of surrounding rock under the influence of confining pressure is obvious when the GSI is small; at this time, the critical plastic shear strain decreases the dilatancy of surrounding rock of the excavation boundary With a certain inhibitory effect.