Abstract: Based on the RITSS large deformation numerical method, using as an example the penetration process of Shengli 9th platform in a complex multi-layer foundation at the Old 174th drilling location, this paper studies the laws governing soil deformation and the foundation bearing capacity profile. The results of the calculation formulas recommended by SNAME are also compared with the results of the RITSS model. The laws governing foundation bearing capacity from the two methods are consistent (having a 10% difference numerically). The effectiveness of RITSS method is proved in modeling the spudcan penetration process in a foundation with a soft and hard interphase. The results show that the RITSS numerical method is an efficient method for modeling soil movement and the laws governing the deformation of each soil layer. The proposed numerical method is capable of obtaining reasonable values for the bearing capacity of a foundation. The peak value of a bearing capacity profile is obtained for sand overlying a clay foundation.