Experimental Study Ananalysis Of Doubile Piles-cap-soil System

When foundation subjected to earthquake action, the bending moment and shear values of joint are at the maximum, in order to avoid premature damage to joint, it need to be constructed at strengthening, in addition, pile- soil interaction system of relations is complexity,、randomness and volatility, the level of the pile bearing capacity of research is becoming more urgent.In this paper, we start with the foundation under horizontal cyclic loading of indoor model test, which includes ordinary double piles foundation, double piles foundation with connection wall and double piles foundation with oblique support. The following results are reached:(1) In terms of the level of capacity, double piles foundation with connection wall is maximum, followed by double piles foundation with oblique support,and ordinary double piles foundation is least;(2) The maximum bending moment of ordinary double piles foundationpile occurs in connection node, additional connection wall and oblique support can make bending moment peak down, it appears in the node of 2D(0.09m)place,and the bending moment of three forms double piles foudation are mainly distributed in the range of top pile 4D(0.18m);( 3) Additional connection wall and oblique support can improve the bending stiffness of double piles foundation effectively, make reverse node of earth pressure down and suppress the bending deformation of pile;(4) The breaking of ordinary double piles foundation occurs in the node,but the breaking of double piles foundation with connection wall and double piles foundation with oblique support occurs in the bottom of connection wall and oblique support.Subsequently, based on the indoor model test,the finite element analysis package,ABAQUS, is used in the paper to simulate the ordinary double piles foundation and double piles foundation with connection wall, which helps to understand the behavior of the them. The following results are reached:(1)The bending moment of the two forms double piles foudation are mainly distributed in the range of top pile 4D(0.18m);the bending moment peak of ordinary double pile foundation at the connection point between the pile and cap,the bending moment peak of double pile foundation with connection wall at the bottom of connection wall, the validity of finite element simulation is verified;(2)Analysis the stress of soil, connection wall make the earth pressurereverse node become not obvious, the effect of horizontal loading depth becomes shallower; connection wall also reduced the influence of horizontal load, which explains the connection wall improves the upper stiffness of the two pile foundation, the foundation bear more horizontal loading, thereby reducing the influence on the soil.