Vertical bearing characteristics of bridge pile foundation under pile-soil-fault coupling action

Based on the Hainan Puqian Bridge, the distance effect and bearing characteristics of bridge pile foundation under the fault-pile-rock interaction were analyzed by the indoor model test and numerical simulation. Research result shows that, in the model test, for a pile foundation with a diameter of 6.3 cm and a length of 60 cm, when the horizontal distance between the fault and the pile foundation increases from 9.45 cm to 22.05 cm, the bearing capacity of pile foundation increases by 26.7%. When the horizontal distance increases from 22.05 cm to 31.50 cm, the bearing capacity increases by only 3.8%, and the influence degree of the horizontal distance on the vertical bearing capacity reduces to 6.5% and may be neglected. When the length of pile foundation is constant and the load is the same, the smaller the horizontal distance, the smaller the change of axial force of pile foundation. The horizontal distance increases from 9.45 cm to 22.05 cm, the side resistance of pile foundation increases by 0.059 kN at the 30 cm of pile foundation length, and the influence degree decreases by 44.5%. When the horizontal distance increases from 22.05 cm to 31.50 cm, the side resistance increases by 0.029 kN, and the influence degree decreases by 8.3%. In the numerical simulation, under the condition that the diameter, length and overburden thickness of pile foundation are 1.5, 30, and 10 m, respectively, when the horizontal distance increases from 1.5 m to 6.0 m, the increment of the bearing capacity reduces from 11.0% to 6.5%. When the horizontal distance increases from 6.0 m to 7.5 m, the increment reduces to 4.9%. When the horizontal distance reduces from 7.5 m to 1.5 m, the axial force of pile foundation decreases gradually along the length direction of pile foundation. When the length of pile foundation is constant and the load is the same, the smaller the horizontal distance, the smaller the change of axial force of pile foundation. When the horizontal distance increases from 1.5 m to 6.0 m, the side resistance of pile foundation at the 16 m of pile foundation length increases by 1.90 MN, and the influence degree of the horizontal distance on the side resistance reduces by 28.0%. When the horizontal distance increases from 6.0 m to 7.5 m, the pile side resistance increases by 0.33 MN, and the influence degree decreases by 5.0%. The results of model test and numerical simulation show that the vertical bearing characteristics of bridge pile foundation are greatly affected by the horizontal distance between the fault and the pile foundation when the horizontal distance is less than five times the pile foundation diameter. When the horizontal distance is more than five times the pile foundation diameter, its influence is smaller or even negligible. The side resistance ratio and influence degrees of the horizontal distance on the bearing capacity and side resistance of pile foundation decrease rapider in the numerical simulation than in the indoor model test. When the horizontal distance is five times the pile foundation diameter, the numerical simulation values reduce by 0.174, 2.2%, and 6.0% compared with the indoor model test values, respectively. Therefore, the numerical simulation result is ideal and can be used as engineering reference.