等温过程路基土体水分迁移特征分析

Analysis on the Moisture Migration of Subgrade Soil with Constant Temperature Condition

以沈哈高速铁路沿线的粘质黄土为研究对象,在恒温状态下进行了开放系统水分迁移试验,试验结果表明:在试件中引起水分迁移最主要的因素是基质势和重力势;土体中各点的含水体积分数从试件底部开始到试件顶部逐渐减小;毛细上升高度与时间呈幂函数增加关系,最终趋向于一个稳定数值;水通量与时间呈对数函数递减关系。基于上述试验,应用有限元法进行数值模拟的结果表明:含水量计算值与试验值基本吻合,表明该模型可应用于模拟地下水在路基中的上升过程;在水分迁移的整个过程中,土中孔隙水压力由土柱底端向上逐渐减小;在水分迁移过程早期,土体内部孔隙水压力的变化比较明显且变化速率较快;随着时间的推移,在水分迁移过程后期土体内部孔隙水压力的分布变化不明显且变化速率较小,当渗流稳定时,孔隙水压力沿着试样高度呈线性分布。

A moisture migration test for unsaturated clayey loess along Shenyang-Ha＇erbin Express Railway for Passenger Line was carried out to investigate the water movement of soil in an open system with constant temperature condition. It is shown that moisture transfer is mainly caused by matrix potential and gravitational potential energy. The water content by volume gradually decreases from the bottom to the top of specimen. Over time the capillary water height increases by the power function and eventually reaches a stable value. The water flux decreases with time by the logarithm function. Based on the model test, finite element method is adopted to simulate the moisture transfer process in soil under isothermal condition. It is found that the numerical results are in good agreement with the experimental data. The model is thereby used to simulate the rise of groundwater in the subgrade soil. During the whole process of moisture movement, pore water pressure gradually decreases from the bottom to the top of sample. The rapid change o{ pore water pressure in the early process contrasts with slow change in the late process. The pore water pressure has a linear change along the specimen when the seepage reaches steady state.