不同应力路径下非饱和黄土结构特性及其本构模型研究

Study on structural characteristics and constitutive model of unsaturated loess under different stress paths

以不同含水率的原状黄土与相应的重塑黄土为研究对象进行等应力比加载试验,探讨黄土在不同应力比三轴试验条件下的结构变化特性,求取非饱和黄土不同应力条件下的综合结构势参数,选择合适的硬化参数建立非饱和黄土的弹塑性本构模型。研究结果表明:原状黄土与重塑黄土的p-εv曲线有明显不同,应力比k相同的原状样较重塑样的体应变εv偏小;原状黄土的结构破坏强度随含水率的增大而减小且与含水量呈幂函数关系,结构性参数mp随球应力p及应力比k的增大而减小,且不同应力比下的结构性参数mp最后几乎稳定在同一水平;原状黄土的mp*εv-p关系曲线中结构性应变mp*εv与应力p表现为双曲线形式,选择合适的硬化参数可建立弹塑性本构模型较好地模拟不同围压与初始含水量下结构性黄土的应力应变特性。

The undisturbed loess and the corresponding reconstituted loess with different water content are studied by stress ratio loading test. The structural variation characteristics of loess under different stress ratios triaxial test was discussed, and the comprehensive structure potential parameters under different stress states were obtained. The elastoplastic constitutive model of unsaturated loess is established by selecting proper hardening parameters. The results show that the p？εv curves of undisturbed loess and remolding loess are obviously different, and the volumetric strain εv of undisturbed loess is smaller than remolding loess with the same stress ratio k. Undisturbed loess structural failure strength decreases with the increase of water content and in power function relationship, Structural parameter mp decreases with increasing spheric stress p and stress ratio k, structural parameters under different stress ratio stable almost at the same level. Structural strain mp＊εv and stress p in the curves of undisturbed loess presents hyperbolic form, to select the appropriate hardening parameter elastoplastic constitutive model can built better simulate stress and strain characteristics of the structural loess under different confining pressure and initial water content.