The big raft foundation has become a main kind of the high-rise building, but the academic study of it should be perfected further more. At the present time, the researching methods for the raft foundation mainly contain prototype foundation testing, model test and finite element analysis. But experimental methods are the characteristic of pertinences and much money, resolutions of it can't be accurately used at other foundation engineering. The FEM method for the whole raft foundation's analysis is so convenience and economic that it may be an analytical way for vital sky-building, even though the foundation soils' physical and mechanical characters are discrete, and the interactions between the foundation, base and superstructure are complex. Lots of its applications have been used to simulate its prototype foundation test closely.Studying the computational method of raft foundation on the base of mechanical characteristic of foundation and soils, the special program of raft foundation design, neatly named as RFDG, has been designed by the secondary development language Tcl/Tk, APDL and UIDL for ANSYS. At the following time, the numerical experiments and case study have been carried out. Through the former analysis, the relations have been sum-up, between the settlement and the subsidiary stress of the raft foundation, and the thickness, depth, and width of the raft. While, through the latter analysis, by the contrast of the 3-D model, the RFDG simulate and the observation, the stress state and settlement have been simulated very well by the RFDG program.In this paper, the basic procedure for the second development of ANSYS has been summarized, especially the use of the Tcl/Tk. At the same time, the method has been applied for other users. |