考虑循环温度驱动的土?水特征曲线滞后模型

在温度、水头等边界条件往复变化时，土体内的水分迁移过程会出现滞后效应。为了模拟非饱和土在经历温度循环时水力特性，提出了一个能够反映滞后效应的经验模型，该模型假定各扫面线的曲线形态与对应边界线相似，因此利用土?水特征曲线中两条边界线的方程，无需引入新的参数，即可得到任意状态出发的扫描线方程。以高岭土为介质，设计了循环温度驱动下的土柱试验，在不透水的土柱内，利用水浴加热的方式使土样一端进行升降温循环。试验结果表明，升温后孔隙水会从高温端向低温端迁移，温度降低到初始状态后，含水率的分布不会完全恢复到初始状态，而是表现出一定的滞后效应。利用该滞后模型进行数值计算，可以较好地反映试验过程中滞后效应对土体含水率变化的影响，并结合已有的砂土、粉土试验结果，验证了该模型的有效性。该模型计算方法简单，易于通过程序实现，可应用于地质处置、供热管道设计等工程问题。

Hysteresis model of soil-water characteristic curves driven by cyclic temperature

The soil-water characteristic curve shows hysteresis when boundary conditions such as temperature and water head change cyclically. To simulate the hydraulic properties of the unsaturated soil under temperature cycle, this paper proposes an empirical model to reflect the hysteresis effect. The model assumes that the curve shape of each scanning curve is similar to the corresponding boundary curve, therefore, using the equations of the two boundary curves, the model is capable of predicting all the scanning curves without introducing new parameters. In this paper, a soil column test using kaolin clay as the medium and dry-wet cyclic driven by temperature is designed. In the impermeable soil column, the water bath is used to make an end of the soil change temperature cyclically. The results show that the pore water will migrate from the high temperature to the low; after the temperature drops to the initial state, the distribution of water content will not completely return to the initial state, showing a hysteresis effect. Using the hysteresis model in numerical calculation can reflect the hysteresis in the water migration process in soil. The existing results of sand and silt also verify the effectiveness of the proposed model. This model is easily to calculating and programming, and is capable of being applied to engineering problems such as geological disposal, heating pipeline design.