Numerical Simulation Study of Bearing Characteristics of Large-Diameter Flexible Piles Under Complex Loads

The majority of the existing calculation methods for determining the ultimate bearing capacity of steel-pipe piles using Chinese criteria are designed for piles with diameters smaller than 2 m. To investigate the bearing capacity of flexible steel-pipe piles with diameters larger than 2 m under combined loading conditions, reveal nonlinear interactions between vertical and horizontal loads, and propose bearing capacity envelopes, in this paper, a numerical method was used to study the bearing capacity of a flexible pile with a diameter of 2.8 m and an embedment length of 72 m under vertical and horizontal loading conditions. First, a numerical model was developed and calibrated using field test results. Then, the effects of vertical pressure on horizontal capacity and lateral force on vertical capacity and uplift capacity of the pile were analyzed. The results indicate that vertical pressure at the top of the pile can nonlinearly reduce its horizontal capacity, but this pressure initially has a slight positive effect on the horizontal bearing capacity before causing a rapid decrease. Conversely, horizontal force negatively impacts both the compressive and uplift bearing capacities of the pile. Finally, depending on the above results, bearing capacity envelopes for piles subjected to vertical and horizontal loads were proposed.