The Elastic-plastic Numerical Analysis Of Pile Foundation In Sand Under Multidirectional Lateral Loadings

The present studies on lateral loaded piles were mostly focused on unidirectional horizontal loading. The horizontal forces in practical problems, such as earthquake loading and wave loading, have multidirectional characteristics. The same problems also exist in the pile groups, and the direction of unidirectional horizontal loading is along the symmetry axis of the pile level layout. It is necessary to carry out the study on pile foundation under multidirectional loading, as well as the pile groups under the unidirectional horizontal loading along the asymmetry axis. In this paper, the numerical simulation method is used to study the pile foundation under unidirectional horizontal loading, multidirectional horizontal loading and unidirectional horizontal loading along asymmetric axis direction. The main parameters of numerical simulation were obtained from the triaxial test.First, the single pile under unidirectional and multidirectional horizontal loading was simulated . The simulation of multidirectional horizontal loading took circular (elliptical) path load method. The displacement along X direction is 10mm, the maximum unidirectional horizontal force is 273N, the maximum horizontal force of circular loading (the maximum displacement ratio of X and Y is 1:1) on X direction was 255N. The maximum horizontal force of elliptical loading (the maximum displacement ratio of X and Y are 1:0.6 and 1:0.2)on X direction are 262N and 270N.It can be evidently seen, under multidirectional loading conditions, the maximum horizontal force on X direction has been reduced remarkably, and the reduction degree increased as the Y direction displacement increasing.Then, the pile groups under unidirectional horizontal loading were simulated. The pile layout of 2x2 was used and the piles spacing was 3D (D is the pile diameter). Under unidirectional horizontal loading, the maximum horizontal force of the front row pile is 598N, the maximum horizontal force of the rear row pile is 488N. This indicated generate the horizontal pile group effect.The pile group effect coefficient of the front row pile and the rear row pile are 0.82 and 0.67 respectively. The pile groups under the load along non-symmetry axis direction were simulated. Under unidirectional horizontal loading along the non-symmetry axis direction with the X-axis angle of 15°and 30°, the horizontal force direction of the pile head and displacement direction is non-coaxial. when the displacement is 10mm and the angle of displacement direction is 15°, the angle of he horizontal force direction of pile 1, pile 2, pile 3 and pile 4 are 16.8°, 12.5°, 17.6°and 11.6°; if the angle of displacement direction is 30°, the angle of the horizontal force direction of pile 1, pile 2, pile 3 and pile 4 are 31.0°, 28.7°, 31.3°and 28.0°. The phenomenon of non-coaxial has obviously seen from the direction of force and displacement. The total level force of the unidirectional loading of non-symmetry axis and symmetry direction is unchange, it indicated that the direction of loading did not affect the total horizontal bearing very muchFinally, the pile groups under multidirectional horizontal loading were simulated. The same as single pile, the maximum horizontal force of the pile has suffered reduction of different degree . Because the horizontal pile group effect, the maximum horizontal force of pile reduced more than that of single pile.