Study of Influencing Factors on Cone Factor for Cone Penetration in Marine Clay

To study the influence of the rigidity index, strain softening, and strain rate on the cone factor of marine clay, cone penetration in clay is simulated on the basis of the finite element method, and an arbitrary Lagrangian-Eulerian （ALE） technique is adopted to control the quality of mesh under the condition of large strain. The difference between the traditional small-strain analysis and the ALE large-strain analysis under the steady state is discussed, and the influences of the rigidity index on the cone factor and the extension of the plastic zone are analyzed. The strain-softening parameters and the strain-rate-controlling parameter for the strain-rate dependency of soil are introduced to analyze the influence of strain softening （sensitivity） and strain rate on the cone factor. In addition, a cone factor expression is proposed considering the influence of the rigidity index, strain softening, and strain rate of the soft soil. The results show that the traditional small-strain analysis greatly underestimates the bearing capacity of clay, whereas the ultimate bearing capacity under large strain increases with penetration depth to finally reach steady state at 12D depth. Moreover, the cone factor and the plastic zone increase with an increase in the rigidity index, and the radial expansion of the plastic zone around the cone tip is closer to the spherical cavity expansion. The sensitivity of the soil increases and the cone factor decreases slightly with a decrease in the strain-softening parameter. The increase in the strain-rate-controlling parameter causes the cone factor to increase significantly, although the increment is independent of sensitivity. In this study, the influence of the rigidity index, strain softening, and strain rate on the cone factor of marine clay is quantified by this expression, which is helpful in evaluating the shear strength of marine clay using the static cone penetration technique.