Spherical Cavity Expansion–Based Method for Cone Factor Considering the Nonlinear Characteristics of Clay

Nonlinear stress–strain relation has attracted much attention in geotechnical engineering, but it is rarely considered in the field of the cone penetration test (CPT). Interpretation formulas for the CPT in soft clays are commonly based on an elastic–perfectly plastic soil model for simplicity. This work carries out numerical and theoretical analyses in an effort to develop an evaluation method for the cone factor focusing on the nonlinear characteristics of soil. Large-deformation finite-element analyses based on an Arbitrary Lagrangian–Eulerian method are performed to investigate the main influencing variables. Variations of cone factors are examined with the rigidity index of the soil, cone roughness, soil yield criterion, and in situ stress anisotropy. Besides that, the nonlinear stress–strain relation shows great influence on the cone factor when using a hyperbolic hardening constitutive model. On this basis, a spherical cavity expansion–based approach for estimating the cone factor is originally proposed for the elastic–perfectly plastic model and then modified to the hyperbolic hardening model. By comparing with the large-deformation finite-element results and existing solutions, good agreement and notable improvement are shown. To ease the proposed method, an analytical solution to the spherical cavity expansion is derived complementally. The practical application of the proposed approach is verified with field CPT data published in the literature.