To investigate the deformation mechanisms of rock under hydrostatic stress, destructive experiments were conducted on sandstone under different levels of hydrostatic stress and stress Lode angles. The results reveal that the shape of the strength envelope on the π plane gradually changes from the shape of the Lade criterion to the shape of the Drucker-Prage criterion with an increase in hydrostatic stress. Normally, there exists a deviation between the strain and stress paths for porous rocks on the π plane, and the deviation decreases with an increase in stress Lode angle and hydrostatic stress. A rock failure hypothesis based on the rock porous structure was proposed to investigate the reasons for the abovementioned phenomena. It was found that the shear expansion in the minimum principal stress direction is the dominant factor affecting the Lode angle effect (LAE); the magnitude of the hydrostatic stress induces the variation of the porous structure and influences the shear expansion. Therefore, the hydrostatic stress state affects the LAE. The failure hypothesis proposed in this paper can clarify the hydrostatic stress effect, LAE, and the variation of the rock strength envelope shape.

为研究岩石在静水应力作用下的变形机制，对砂岩在不同静水应力水平和应力探脉角下进行了破坏性试验。结果表明，随着静水应力的增加，π平面上强度包络线的形状逐渐从Lade准则的形状变为Drucker-Prage准则的形状。通常情况下，多孔岩石在 π 平面上的应变路径和应力路径存在偏差，并且该偏差随着应力波德角和静水应力的增加而减小。提出基于岩石多孔结构的岩石破坏假说来研究上述现象的原因。研究发现，最小主应力方向的剪切膨胀是影响洛德角效应（LAE）的主要因素；静水应力的大小引起多孔结构的变化并影响剪切膨胀。因此，静水应力状态会影响 LAE。本文提出的破坏假设可以阐明静水应力效应、LAE和岩石强度包络线形状的变化。