Abstract：From the point of seepage mechanism，3D nonlinear seepage analysis is made for the case in which Darcy law is not available. The controlling factor and formula representation of nonlinear seepage are discussed. 3D nonlinear seepage analysis is carried out on rock-soils with FEM，based on an empirical nonlinear relation between seepage velocity and hydraulic gradient. The nonlinear seepage controlling equations are derived by using Galerkin FEM，and numerically solved by direct iteration. Some issues，including the criteria of iteration convergence，improvement of the calculation precision，and acceleration of convergence，are discussed. An explanatory example is given，and the numerical result is very close to theoretical solution. The study result shows that the presented approach is of simplicity for programming，high computational efficiency and fast convergence.
