Abstract: According to the current specifications, the undrained shear strength of clay is interpreted based on the recommended cone factor derived from empirical values. However, this factor has limitations in terms of its empirical nature. Moreover, the existing cone factors are derived from the elastic-perfectly plastic model, without considering the nonlinear characteristics of soil deformation. To tackle these issues, a simulation of the cone penetration process is performed using the finite element software ABAQUS. The cone resistance q_c is assessed using the hyperbolic hardening model for clay, and the arbitrary Lagrangian Eulerian (ALE) remeshing technique is employed to prevent grid distortion. The finite element results show that the factors such as soil stiffness, cone roughness and failure criteria affect the cone factor. Furthermore, the undrained expansion for a circular cavity is simulated using the finite element method to obtain the expression for the ultimate bearing capacity factor. Subsequently, an equivalent conversion relationship between the smooth cone tip resistance and the limit expansion pressure of the cavity is established. Finally, a verification against an engineering case is conducted.