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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。
Soft rock has typical elastic-plastic deformation characteristics, and at the same time, soft rock is considered as structural overconsolidated clay because of its strong internal cementation. The variation of soft rock residual strength with confining pressure is a significant characteristic of the mechanical properties of soft rock after peak, which is of great significance in practical engineering. By extending the concept of void ratio, we can consider the structure and overconsolidation of soft rock simultaneously, and give a reasonable development. By introducing the concept of structural lower loading surface, a structural lower loading surface model of soft rock is established on the basis of the Cambridge model. The model can reflect the effect of confining pressure on the structural failure rate of soft rock, and finally leads to the difference of the residual structural properties retained by the soft rock under the different confining pressure during the stage of residual strength deformation, so that the residual strength of soft rock changes with the confining pressure. Comparing the theoretical calculation results with the triaxial compression and drainage test results of soft rock, the results show that the model can describe the strain hardening and softening properties of soft rock and the volume-deformation dilatancy characteristics well, and can well describe soft rock The residual strength changes with the confining pressure of this mechanical properties, and give a reasonable explanation.