兰州压实黄土水分迁移规律试验与数值模拟

Experiment and Numerical Simulation Analysis of Water Migration of Lanzhou Compacted Loess

为了研究试坑浸水试验过程中水分迁移规律,依托兰州市填沟造地工程,首先对压实黄土进行一维入渗试验并应用改进的浸润锋前进法获得压实黄土的非饱和渗透系数函数;然后依据非饱和土体水分运动理论,应用SWMS-2D程序建立了室内试坑浸水的土体水分轴对称二维数值模型,利用该模型并应用求解Richard方程的数值方法,对可以清晰观测浸润锋的室内试坑浸水试验进行了模拟;最后对比了一维入渗和二维入渗的差别。结果表明:数值模拟法能较好地预测室内试坑浸水试验中的浸润锋迁移规律,说明应用一维土柱获得的非饱和渗透系数函数以及求Richard方程数值方法的可靠性;随着试坑直径的增大,试坑中心线下浸润锋迁移规律趋向于一维入渗;已有近似解析模型在预测试坑中心线下水分场变化规律是可靠的,数值计算方法能模拟水平入渗范围。

In order to study the law of water migration during the immersion test,this paper relied on the Lanzhou landfill project,firstly carried out one-dimensional infiltration test in compacted loess and applied the improved wetting front forward method to obtain the unsaturated hydraulic conductivity function of compacted loess.Then based on the theory of unsaturated soil water movement,the SWMS-2D program was used to establish the axisymmetric two-dimensional numerical model of the indoor pit immersion test.Using the model and applying the numerical method of solving the Richard equation,indoor immersion test in which the wetting front could be clearly observed was simulated.Fi-nally,the difference between one-dimensional infiltration and two-dimensional infiltration was compared.The research shows that the numerical simulation method can well predict the migration law of wetting front in the indoor pit immersion test.It proves that the unsaturated hydraulic conductivity function obtained by applying the one-dimensional soil column and the numerical method of calculating the Richard equation are reliable.Numerical experiments show that with the increase of the diameter of the test,the migration law of the wetting front under the center line of pit tends to one-dimensional infiltration.The approximate analytic model is reliable in the change of the water field under the center line of the pre-test pit.The numerical simulation can well predict the wetted range in horizontal direction.