岩体离散裂隙网络的非饱和渗流数值分析

Numerical analysis of unsaturated seepage flow in discrete fracture networks of rock

针对裂隙岩体的非饱和渗流问题,基于离散裂隙网络模型并结合非饱和Darcy定律、Richards方程、非饱和本构模型以及Signorini型饱和-非饱和互补溢出边界,提出了离散裂隙网络非饱和渗流问题的数学模型。采用有限单元法建立了裂隙网络非饱和渗流模型的数值求解格式和对应的迭代算法。通过与矩形坝稳定渗流、一维竖直裂隙非饱和入渗以及室内二维瞬态排水渗流的试验、数值及理论结果对比分析,验证了文中算法的有效性;根据流量等效原则,指出了裂隙网络模型应用于求解连续介质非饱和渗流问题的有效性。验证了该算法对于求解裂隙边坡降雨入渗问题的可靠性,揭示了降雨入渗过程裂隙网络流量分布的非均匀性及裂隙产状对降雨入渗流动具有重要的控制作用。

A mathematical model based on the discrete fracture network model is developed for the problem of unsaturated seepage flow in fractured rock. The saturated-unsaturated flow behavior is governed by Darcy＇s law, Richards＇ equation, the constitutive relationships and the complementary condition of Signorini＇s type on the potential seepage surface. The finite element method is used to establish a numerical solution scheme and a corresponding iterative algorithm for the unsaturated seepage flow model of the fracture network. The effectiveness of the proposed algorithm is verified by comparing with the rectangular seepage, the one-dimensional vertical fracture unsaturated infiltration and the indoor two-dimensional transient drainage seepage test, numerical and theoretical results. According to the principle of flow equivalence, the effectiveness of the fracture network model in solving the problem of unsaturated seepage in continuous media is highlighted. It proves that the algorithm is effective to solve the problem of rainfall infiltration in the fissure slope. The nonuniformity of the flow distribution of the fracture network and the occurrence of the fractures show important control on the rainfall infiltration flow.