动态土水特征曲线滞后模型研究

土水特征曲线是描述非饱和土力学特性必不可少的方程,它的最大特点就是存在滞后效应,尽管目前已经建立了很多的土水特征曲线滞后模型,但这些模型都是针对平衡条件建立的。现有的理论和试验研究已经证实,土水特征曲线存在动态效应,与静态土水特征曲线相比,相同的饱和度时,动态土水特征曲线的吸力在干燥过程中要更大,而湿化过程中则更低。为了描述动态条件下土水特征曲线,首先从热力学的基础理论出发,探讨了动态效应的理论基础,并从熵增不等式中得到了动态的土水特征曲线方程。基于所得方程,利用边界面塑性理论,建立了可以预测任意扫描线的土水特征曲线模型。通过与已有的试验结果进行对比,表明模型可以很好地预测土体在干燥和湿化不同过程中的扫描线变化。所得结果可以用于解释一些实际问题,比如降水引起的沉降和降雨诱发滑坡等。

Hysteresis model for soil-water characteristic curve under dynamic conditions

The soil-water characteristic curve(SWCC)is essential to describe the behavior of unsaturated soils.The capillary hysteresis is an important effect that should be accounted in the equations for SWCC.The existing SWCC models are mainly based on the equilibrium condition.However,there is ample theoretical and experimental evidence that the curve is not unique under dynamic conditions.The dynamic capillary pressure is larger than the static one in drainage and smaller in wetting.A thermodynamic theoretical basis for the SWCC under dynamic conditions is given.A dynamic capillary hysteresis model is developed based on the bounding surface plasticity.Provided that the main drying and wetting curves have been experimentally determined,the model is capable of predicting all the scanning curves.The model predictions are compared with the existing experiments found in the literatures,showing a good accordance with the test data for both the drying and wetting conditions.The results can then be used to explain some practical problems such as foundation settlement and slope stability.