压力控制的圆孔扩张数值模拟分析

受沉积历史的影响,实际工程中土体的初始应力往往呈各向异性,此时传统圆孔扩张理论的假定条件不再成立,故其适用性也受到限制。借助于FLAC有限差分数值软件,建立了以压力为圆孔扩张边界的二维圆孔扩张模型,从圆孔的变形、孔周土屈服范围、圆孔扩张产生的超静孔水压力分布等方面进行分析,获得在初始应力各向异性的条件下压力控制圆孔扩张过程土体响应规律。计算分析结果表明,初始应力各向异性时,压力控制的圆孔扩张孔口径向位移、塑性区分布、超静孔隙水压力影响范围各个方向不相等;塑性区的分布具有明显的方向性,塑性区最大半径位于孔周土体初始大主应力方向上,并且其值比在相同的扩张压力作用下各向同性初始应力条件下的塑性区半径大,因此传统的初始等应力条件下位移控制的圆孔扩张理论用于分析各向异性初始应力的工程是偏于不安全的。

Numerical simulation of pressure-controlled cavity expansion

The traditional cavity expansion theory, which is based on the isotropic initial stress in soil layer, could not be used to the situation with anisotropic initial stress in soil layer. A two-dimensional undrained numerical model is conducted to simulate the pressure-controlled cavity expansion process with anisotropic initial stress. Through analyzing the cavity shape, the distribution of plastic zone and excess pore water pressure, the characters of the pressure-controlled cavity expansion with anisotropic initial stress is obtained. The results indicate that the radial displacement, plastic zone and excess pore water pressure around the cavity is not equal in all directions in case of pressure-controlled cavity expansion with anisotropic initial stress, which is different with the traditional cavity expansion. The results also show that the plastic zone of cavity expansion with anisotropic initial stress is larger than that of cavity expansion with isotropic initial stress. It is concluded that it would be unsafe if the traditional cavity expansion theory based on the isotropic initial stress supposition is used to analyze projects with anisotropic initial stress.