二元介质模型在黄土增湿变形分析中的应用

Application of binary medium model in deformation analysis of loess during wetting

在作者建议的二元介质模型中,黄土的变形模量随饱和度的增加而减小,当饱和度与吸力的关系已知时,模量将随孔隙水压力的增大而减小。在此基础上,文中推导了增量型的广义有效压力公式,其孔隙水压力与应力张量成正比,从而不再是标量。文中将上述公式代入平衡方程,推导了不用初应变法而算出湿陷变形的直接算法,并编制了孔隙水压力与土骨架变形的耦合分析有限元程序,用于室内单轴压缩试验和现场荷载板浸水试验的计算,得出了合理的计算结果。

In the binary medium model for loess proposed recently by the author, the deformation moduli of loess decrease with the increase of saturation degree. When the relationship between saturation degree and suction is known, these moduli decrease with the increase of pore water pressure. On this basis, a generalized effective stress equation in incremental form {Δσ}={Δσ'}=Ct{σ} Δuw is proposed in this paper. Unlike the traditional definition of pore water pressure increment Auw, the second term in the right side of this equation is proportional to stress tensor {Δσ}, therefore it is no longer a scalar variable. In addition, the coefficient Ct becomes a negative quantity for collapsible soils. After substituting this equation into the force equilibrium equation, a direct method of wetting deformation computation is formulated instead of commonly used indirect method, known as initial strain method. A 2-D finite element program for coupled pore water pressure and deformation analysis is compiled accordingly. Numerical simulation for both laboratory 1-D compression test and field water impounding test of loess foundation under a loaded circular footing shows that the behaviors of loess under coupled action of loading and wetting are reproduced quite well.