Model Tests And Analytical Research On Batter Pile Foundation Under Lateral Loading

Batter pile group is a basic foundation form frequently applied in large offshore structures. Under the combined loads of self weight, wave, wind and ship, batter pile group is often subject to the joint actions of axial load, horizontal force load and torsion load, among which the horizontal load is the basic main form of load. In present pile foundation designs, the impact of axial load on the horizontal bearing capacity of foundation piles is generally not taken into account; thus, the actual load sustained by foundation piles fails to be correctly reflected.In view of the above problem, this paper carries out a serial of physical model experiments of batter pile foundation, by using large scale geotechnical physical model experiment system of Zhejiang University. Such model experiments include four groups of single piles and one1x2pile group foundation of batter piles. Meanwhile, batter pile driving equipment and static loading equipment are developed to facilitate those model experiments. As a result, pile shaft bending moment distribution curves and soil surface load displacement curves under different load are obtained; it is also found out that the horizontal bearing capacities of positive batter piles, vertical piles and negative batter piles are decreasing in turn, and that axial tension reduces while axial pressure improves the horizontal bearing capacity of batter piles. Therefore, for the better and more accurate calculation of the horizontal bearing capacity of batter piles, this paper introduces into the p-y curve of vertical piles a correction factor which takes account of soil quality and batter pile inclination angle.This paper builds a batter pile passive failure wedge model which takes the axial load effect into consideration, and obtains a batter pile side extreme horizontal soil pressure reaction calculation formula. By introducing the calculation formula into the p-y curve, a new p-y curve expression which considers batter pile inclination and axial load effect is brought up. Both the results of model experiments referred to in literature and the result of model experiment obtained in this paper verify the rationality of the abovementioned p-y curve expression. Last but not least, a new load calculation method of batter piles group foundation is put forward. The significance of this paper lies in that the research result provides support for the design of the batter pile group foundation of large offshore structures.