考虑围压依存性的软岩结构性下加载面模型

软岩具有典型的弹塑性变形特点,同时由于其内部的胶结作用具有较强的结构性,因此将软岩视作结构性超固结黏土。软岩残余强度随围压变化是软岩峰后力学特性的一个显著特性,在实际工程中具有显著的意义。通过对孔隙比之差的概念进行扩展,使之能够同时考虑软岩的结构性和超固结性,并且给出合理的发展式。通过引入结构性下加载面的概念,在剑桥模型的基础上建立起软岩的结构性下加载面模型。该模型能够反映围压对软岩结构性破坏速率的影响,最终导致不同围压下软岩达到残余强度变形阶段时所保留的残余结构性存在差异,使得软岩的残余强度随围压变化。将理论计算结果与软岩的三轴压缩排水试验结果进行对比分析,结果表明该模型能够较好的描述软岩的应变硬化和软化特性及体积变形剪胀特性,同时能较好的描述软岩的残余强度随围压变化这一力学特性,并给出合理解释。

Structured subloading yield surface model for soft rock considering confining pressure

Generally soft rock behavior is characterized by elasto-plastic deformation with heavily inherent cementation, which can be regarded as structured overconsolidated soils. The residual shear strength of the soft rock will be influenced by confining pressure which is significant during the practice. The concept of the difference of void ratio is extended in order to contain the overconsolidation ratio and the structural parameter. A reasonable development equation for the structural void difference is given. By introducing the concept of structured subloading yield surface, the structured subloading Cam-clay model for soft rock is proposed. In the proposed model the confining pressure will influence the structural damage ratio, and the residual structural parameter will be different under various confining pressures. By comparing the drained triaxial test results of the soft rock with the theoretical calculations, it is shown that the model can describe accurately the stress-strain relationships and the deformation features of the soft rock. Moreover, the phenomenon that the residual strength of the soft rock changes with confining pressure can be explained reasonablly by the proposed model.