Numerical Simulation and Application of Zero-Thickness Contact Surface Element with Variable Shear Stiffness on Pile Foundation

In this study, a contact surface constitutive model with zero-thickness unit and variable shear stiffness was improved based on the statistical damage constitutive model. The model parameters were derived by means of the shear stress-shear displacement curve of the pile-soil contact surface, and the model parameters under different normal stresses were obtained by the linear interpolation method. At the same time, the influence of the interpolation interval range on the model parameters was explored. The shear stiffness adjustment factor was introduced, and the improved pile-soil contact surface constitutive model was applied to the numerical simulation of pile-soil contact surface shear calculations using the fish language embedded in FLAC 3D, and the variation of monopile bearing characteristics and ultimate bearing capacity were investigated and analyzed. The results show that the improved contact surface constitutive model is able to reflect the nonlinear variation of shear stiffness, and that different normal stresses correspond to different fitting parameters, demonstrating the depth effect of the model. The accuracy of the model parameters reduces as the interpolation interval increases, and the interpolation results are more accurate when the interval range is smaller. The numerical model accurately simulates the pile-soil contact surface shear calculation and the monopile bearing calculation, and the simulation results of the ultimate pile bearing capacity are closer to the results computed by the equations in the Chinese code. At the same time, the variation law of pile axial force and pile lateral frictional resistance along the depth direction and the variation of pile ultimate bearing capacity under different working conditions are reasonable, which shows the validity of the contact surface principal structure model and the reasonableness of numerical calculation in this study.

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