Numerical analysis of horizontal cyclic responses of large-diameter pipe piles under undrained conditions based on effective stress method

Based on the effective stress principle and clayed bounding surface plastic constitutive model, a material subroutine VUMAT suitable for the undrained analysis in ABAQUS/Explicit was developed, and the effects of the cyclic amplitude and pile diameter on the horizontal responses of large-diameter monopiles in soft clay were studied. The results show that the subroutine can effectively simulate the accumulation characteristics of the pore pressure and displacement of the soil and the stiffness degradation behavior of the clay under cyclic loads. The number of cycles has an approximately linear relationship with the pile's cumulative deformation at the mudline, and the deformation is affected by the load amplitude ratio, the degeneration of unloading stiffness has a power function relationship with the cumulative deformation, and the degeneration increases with the increase of pile diameter. For large-diameter monopiles, the excess pore pressure tends to accumulate at the pile bottom, whose cumulative amplitude is controlled by the cyclic amplitude ratio. However, the pile diameter is not sensitive to the accumulation of excess pore pressure, and the influence area increases significantly when the pile diameter increases. © 2023 Central South University of Technology. All rights reserved.