Abstract:In general,the determination of the failure mechanism for the inhomogeneous subsoil plays an important role in predicting the ultimate bearing capacity. Basing on Duncan-Chang model,a finite element program is compiled to search for the failure mechanism of the inhomogeneous subsoil. Some in-situ loading tests are performed in Tianjin New Harbor area and the experimental data are compared with the computational results from the finite element methods. The reliability of the finite element program is verified through the comparison. By virtue of numerical analyses,the failure process can be reproduced,and the plastic deformation zone and the most-probable rupture surface in the inhomogeneous subsoil are found. It has been found that under the ultimate load the inhomogeneous subsoil exhibits the characteristics of general shear failure or local shear failure. The plastic strains firstly appear on the edge of the footings. With increasing of the load,the plastic zone expands and joints together at last. The appearing of the continuous plastic zone means that bearing capacity failure occurs in the subsoil,and the bearing capacity of the foundation has reached to its ultimate value.