Abstract: 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.

Key words: fracture network, unsaturation, seepage flow, finite elements