初始应力各向异性状态下圆柱孔扩张机制分析

采用静止土压力系数K0描述土体初始应力各向异性程度，建立了压力控制边界条件的柱孔扩张数值模型，分析压力为边界条件的圆柱孔扩张特性。计算结果表明，初始应力条件各向异性时，柱孔周围的土体的径向位移是不相等的，扩张后的柱孔呈椭圆形，初始应力各向异性是柱孔非对称扩张的内在原因；塑性区的分布具有明显的方向性，塑性区最大半径位于柱孔周围初始大主应力方向上；在相同的扩张压力下，随不排水抗剪强度增加，土体的塑性区减小，且土体初始应力各向异性造成的土体塑性区分布各向异性程度也随之减小；在相同的扩张压力下，柱孔初始应力越大，其塑性区范围越大，且土体初始应力各向异性造成的土体塑性区分布的各向异性程度也越大。

Mechanism of cylindrical cavity expansion under anisotropic initial stress state

Anisotropic initial stress is described by the coefficient K0 of earth pressure at rest. A two-dimensional elastoplastic numerical stimulation is performed to analyze the pressure-controlled cylindrical cavity expansion with anisotropic initial stress. The results indicate that the radial displacements around the cavity are unequal in different directions and the cylindrical cavity expansion is asymmetrical ellipse due to anisotropic initial stress. The largest range of plastic zone develops in the direction of the maximum principal initial stress and the plastic zone has devious directivity. The results also demonstrate that the undrained shear strength and initial stress level have significant effect on the pressure-controlled cavity expansion process with anisotropic initial stress. With the undrained shear strength increasing, both the largest range of plastic zone and the effect degree of anisotropic initial stress on the anisotropic plastic zone distribution decrease under the same expansive pressure. With the increasing of initial stress, not only the largest range of plastic zone but also the effect degree of anisotropic initial stress on the anisotropic plastic zone distribution increase.