Abstract:Based on the variation principle,the composite element method(CEM) is studied for seepage analysis considering discontinuous surfaces and drainage holes. The CEM has the ability to contain discontinuous segments such as faults and joints within elements. In this way the discontinuous surface can be simulated explicitly without special elements deployed along the discontinuous surface. The drainage holes are looked as materials with high permeability and treated as “air sub-elements” set in the composite element. By the CEM,the case of discontinuities crossed by drainage holes can be well modeled while the discontinuities and drainage holes needn¢t to be meshed. Furthermore,the mesh can be the same when the position and number of the discontinuities and drainage holes are changed. If there are no discontinuities or drainage holes,the CEM will automatically be degenerated to the conventional finite element method(FEM). Compared with the FEM,the CEM will make the mesh generation work relatively convenient and will improve the efficiency of calculations. The validity and reliability of the CEM are verified by the given examples.