多孔介质岩土材料剪切带孔隙特征研究(2)——最大孔隙比分析

ANALYSIS OF VOID CHARACTERISTICS IN SHEAR BAND OF POROUS MEDIA (2):MAXIMUM VOID RATIO

在流动剪切应力为残余剪切强度时,对剪切带内部的局部孔隙比和平均孔隙比进行了理论分析。对于应变软化阶段剪胀的岩土材料,基于梯度塑性理论验证了在剪切带内部存在最大孔隙比的客观事实,最大孔隙比具有两层含义,即局部(和坐标有关)最大孔隙比和平均最大孔隙比,分别解释了相关的实验现象。对影响剪切带内部平均最大孔隙度的因素进行了分析;给出了剪切软化模量、残余剪切强度及扩容角对剪切带内部最大孔隙度的影响规律。在软化过程中,剪切带中部最大孔隙度逐渐增加,直至残余强度剪切带中部最大孔隙度达到最大值。研究结果为流固耦合多孔介质岩土材料的稳定性研究奠定了初步的理论基础。

Local void ratio and average void ratio in shear band are investigated as residual shear strength is reached. For quasi-brittle materials that dilate, some experimental results show that maximum void ratio occurs in critical state of the shear band. Further discussion is made based on gradient-dependent plasticity with consideration of the effect of microstructures. Local maximum void ratio is different from average maximum void ratio. Local means are dependent on coordinates, while the average stands for the whole shear band. Influences of dilation angle, initial void ratio with shear localization initiated, residual shear strength, shear elastic modulus and shear softening modulus on the average maximum porosity and on the maximum porosity are analyzed. In the process of residual deformation, maximum void ratio is reached and remains constant. The presented conclusion lays a foundation for problem of instability involved in coupling of fluid and porous media.