Numerical Simulation of Force and Soil Displacement of Inclined Long-short Composite Piles under Foundation Pit Excavation

The foundation pit support model was established with the software Midas GTS NX to simulate and analyze the changes of soil displacement of foundation pit, horizontal displacement and bending moment of pile body under different inclined long-short combined pile supports during the excavation process of foundation pit, and to explore the influence of pile length distribution of combined pile and inclination angle of long piles on the support effect. The results show that during the excavation process of the foundation pit, with the increase of the excavation depth, increasing the inclination angle of the long pile to a certain extent can effectively reduce the soil deformation and the horizontal displacement of the pile body, and the maximum bending moment of the pile body below the excavation surface decreases with the increase of the inclination angle of the long pile. When the total pile length is constant, there is a critical value for the optimal pile length distribution affected by the inclination angle of the long pile. Below the critical value of the inclination angle of the long pile, the optimal pile length distribution is affected by the change of the inclination angle. Above the critical value of the inclination angle of the long pile, the longer the long pile is, the better the support effect is. At the same excavation depth, the horizontal displacement of the pile body is related to the inclination angle of the long pile, and the influence of the inclination angle of the long pile on the pile body displacement above the excavation surface is greater than that below the excavation surface. The maximum bending moment of the part of the pile body below the excavation surface is proportional to the pile length.