高饱和条件下水-力-化耦合模型及数值模拟

Hydro-mechanical-chemical coupling model and numerical simulation under high saturated condition

填埋场底部黏土垫层特性对其长期防渗隔污服役性能的有效发挥具有极其重要的作用。针对实际堆场中黏土屏障呈现出的高饱和状态,将液相(孔隙水)与气相(闭塞气泡)视为混合流体,通过分别建立土体应力平衡方程、混合流体质量守恒方程及溶质质量守恒方程,综合考虑土颗粒-孔隙流体-溶质间的相互作用机制,推导得到了高饱和度条件下,溶质在黏土防渗层中运移的水-力-化全耦合模型,能够实现多物理场耦合作用时土层变形量、混合流体压力及溶质溶度随时空分布的直接精确求解。采用多场耦合有限元分析软件COMSOL对所建模型开展数值模拟,结果表明,模型结果与Peters所得结果吻合较好;黏土垫层中可压缩性气体的存在延缓了超孔隙流体压力的消散,加大了土层的沉降量,对溶质在防渗黏土层中的运移进程起到了显著的阻滞效果。

The behavior of clay liner at the bottom of landfill site plays an important role in the effective performance of its long-term seepage and pollution control. In view of the high saturation state of soil barrier in the actual yard, the liquid phase(pore water) and gas phase(block bubble) are considered as mixed fluid in this study. By establishing soil stress equilibrium equations, mixed fluid mass conservation equations, and solute mass conservation equations, the interaction mechanism of soil particle, pore fluid, solute is considered comprehensively;and a hydraulic-mechanical-chemical fully coupled model for solute transport in high saturated clay liner is presented. The model can directly and accurately solve the deformation of soil layer, mixed fluid pressure and solute distribution with time and space. The multi-field coupled finite element analysis software COMSOL is used to carry out numerical simulation on the model;the results show that the model results are in good agreement with the results obtained by Peters. Meanwhile, the existence of compressible gas in the clay liner delayed the dissipation of the excess pore fluid pressure, increased the settlement of the soil layer, and had a delayed effect on solute transport in the clay liner.