【摘要】 多孔介质中的流动问题,与孔隙介质的特性,含水量状态以及含水量的变化历史密切相关。基于毛细循环滞回理论模型,考虑含水量变化历史对土水特征关系的影响,在开发的U-DYSAC2有限元程序中进行了相应的数值实施。在试验给定的初边值条件下进行了非饱和渗流模拟分析,并将模拟结果与实测数据比较,表明在压力边界条件反复变化下,考虑滞回效应能获得更接近实测的结果,证实该模型在模拟各种循环变化条件下非饱和土渗流初边值问题的适用性与必要性。对入渗重分布反复变化条件下非饱和土柱流动的数值模拟表明,考虑滞回与不考虑滞回条件下,含水量、孔隙水压力和湿峰的迁移的预测在入渗后的重分布过程差异较大。考虑滞回效应时,土柱上部的脱湿速率、下部的吸湿速率比不考虑滞回时要低。从而证实了非饱和多孔介质中的土水状态依赖于含水量变化,而且强烈依赖于土体的水力路径变化。因此,循环边界条件变化下,毛细滞回效应在非饱和渗流模拟中的影响显著,必须加以考虑。更多还原

【Abstract】 Unsaturated flow problem in a porous medium is closely related to the characteristics of porous medium,soil moisture state and its drying/wetting history.Based on capillary cyclic hysteresis model which considers the effect of the history of water content on the relation of soil water characteristics,a modified U-DYSAC2 finite element program is developed to simulate the unsaturated seepage problems.Unsaturated flow analysis is done under experimental conditions.Compared the simulated results with experimental data from the literature,the results with hysteresis effect are much nearer to the data from the tests undergoing repeating changes of pressure boundary conditions.Hence the applicability and necessity of the numerical model is verified being capable for modeling the intial boundary problems of unsaturated seepage.Subsequently,an example is shown for flow analysis in a soil column subjected to complicated infiltration redistribution history.The results show that the discrepancy of water content,pore water pressure and movement rate of wetting front in the column is large during redistribution process considering hysteresis effect and non-hysteresis effect respectively.It is shown that rate of drying in uppper layer and rate of wetting in lower layer considering hysteresis effect than that of nonhysteresis analysis.The simulated results confirm that soil moisture state in unsaturated porous media is not only dependent on water content,but also related to hydraulic path in porous medium.Hence,under cyclic change of boundary conditions,it is necessary to consider hysteresis effect in modeling unsaturated seepage problems.更多还原