结构性黄土双轴压缩试验的离散元数值仿真分析

Numerical simulation of biaxial tests on structured loess by distinct element method

通过建立胶结强度与初始含水率之间的关系将含水率引入胶结接触模型,并将其应用于饱和重塑土和不同含水率结构性黄土离散元试样的常规双轴试验数值模拟中。结果表明:结构性黄土离散元试样双轴试验的宏观力学行为与天然结构性黄土室内三轴试验结果相似。即围压越低,含水率越低,则试样越容易表现出应变软化和剪胀;反之则试样越容易表现为应变硬化和剪缩。该宏观力学行为与试样粒间胶结破坏密切相关。即围压越低,含水率越低,则试样固结过程产生的胶结破坏越少,后续胶结破坏对试样宏观力学行为影响较大,试样越容易表现出应变软化和剪胀。

A relationship between the bond strength and the initial water content is established and used to incorporate water content to a bond contact model. Then using this model, various numerical biaxial tests on remolded and structured loess samples with different water contents are carried out by means of the distinct element method. The following conclusions can be drawn from these simulations. The macro-mechanical behaviors of biaxial tests on numerical and natural loess samples are similar. That is, as the confining pressure and initial water content decrease, the samples exihibit much strain softening and shear dilatancy. As the confining pressure and initial water content increase, however, the samples perform much strain hardening and shear contraction. The macro-mechanical behaviors are associated with the inter-particle bond breakage. Because fewer bonds of samples with lower confining pressure and initial water content are broken in the consolidation, the bonds affect biaxial compression more and the samples exhibit strain softening and shear dilatancy relatively.