Experimental Study On The Engineering Features Of The Multi-pile With Lateral Surcharge

A large area surcharge next to the pile has a great impact on the deformation of the pile,for example,pile and soil produce differential settlement with surcharge leads to the frictional resistance on the pile body, lateral displacement of foundation soil squeezes the pile and causes the lateral displacement and deformation of pile. This paper studied the force deformation of piles with the lateral surcharge through indoor model tests, and respectively analyzed the size of side surcharge, pile material, pile length and the different limited conditions. And the focus of this paper analyzed the p-s curve of soil, lateral displacement in the top of the pile, lateral difference along the socket pile and friction pile, earth pressure difference along the socket pile and friction pile, multi-type pile moment, axial force and the different friction resistance along the pile when loading and unloading through comparison. And the conclusion is as follows:(1)When the lateral surcharge increased to a certain size, the position of maximum stress of pile should not be moved down, and the maximum stress value is plummeted from 10 kPa to 40 kPa. And when the load increased after that, this maximum value is hardly changed, and the whole pile stress would not change.(2)When the foundation is in a situation of the elastic equilibrium, the stress of the friction pile body is generally larger than the one of the socket pile with a larger lateral binding; when soil is in the situation of the shear deformation stage, socket pile stress grows faster than the friction pile, and then "actively" bears the binding force on the soil, and the stress of the pile body is also larger than the friction pile, playing a stronger constraints effect on soil.(3)As the load increases, the increasing rate of the bending moment of the rigid pile body is less than the one of the flexible pile, and the maximum position of bending moment has the trend of moving down. When the load reaches a certain value, the bending moment of the rigid socketed-pile is no longer increased, and the bending moment of flexible rock pile above the pile body is not increased any more, and the part of the body below half of the pile is still regularly increased. During the uninstalling process, the change of the bending moment at the final stage of discharge is larger than the aggregation of the early changes of the bending moment, showing that the rebound of soil in the uninstall process is concentrated at the surface during the uninstalling process.(4)In the initial process of the loading, the axial force of the pile body continues to increase along the pile, peaking at-700mm; the second load is before the 75 KN, and the axial force value is positively changed when distance between the rigid socketed-pile and the top-pile is more than 2/3, however, the axial force continued to negatively increased, which indicates that the load effects within the soil is gradually moved down; after 75 KN, the entire axial force value of the pile body negatively grows and maintains a constant situation; axial force of the flexible socket pile appears the "S" and the axial force of the flexible friction pile appears the shape of "contrary 3". With the load increases, the axial force changes are more obvious in the upper part of the pile.(5)As the load increases, the negative friction on upper half of rigid short pile negatively increases. Due to the compression of the lower part of the soil, the negative friction occurred in the lower pile, because of the negative friction in the upper pile, rigid long pile piercing downward, causing a positive friction in the lower part.