Abstract: Based on the slip-line in plastic mechanics, equilibrium differential equations of a foundation in limit equilibrium state under a strip footing are deduced. using the finite-difference method, the finite difference formula in limit equilibrium state is given. Combining with the boundary conditions, a program for computing the bearing capacity is written that can compute the slip-line field and the corresponding bearing capacity considering the depth of embedment, the unit weight, the internal frictional angle and the roughness of the foundation at the same time. The calculating results of the bearing capacity factor Nγ are shown with the change of the internal frictional angle. The influences of the depth of embedment, the unit weight, the internal frictional angle and the roughness of the foundation on the shape of slip lines and the bearing capacity, are generally discussed; and some valuable conclusions are drawn.

Key words: slip line, limit equilibrium method, finite difference method, bearing capacity