Research On Mechanical Characteristics Of Pile Raft Composite Foundation In Deep Water And Thick Clay Areas

There are many islands in our country, straits and bays and other natural moat hinder its connection to the mainland transport network. With the continuous economic development in recent years, constructing large bridges to make neighboring islands connect to the transportation network of mainland is particularly urgent and important. With/without raft of rigid pile composite foundation have been widely used in high-speed rail in the soft ground, but both the engineering examples and indoor test are the lack about these two forms of composite foundation used in transoceanic bridge’s foundation in the deep water and thick clay areas.This paper is mainly based on indoor centrifugal model test and numerical simulation, researching the mechanical characteristics of pile raft composite foundation through comparative analysis the variation of settlement, pile-soil stress ratio, pile-soil load sharing ratio and other parameters of with/without raft of rigid pile composite foundation, and researching the mechanical characteristics of pile raft composite foundation by the finite element software under different thickness of raft and different thickness of cushion. The main conclusion is as follows:(1) In the centrifuge test loading process of with/without raft of rigid pile composite foundation, the settlement law of foundation is consistent, but the former is only43.8%of the latter. The pile-soil stress ratio of rigid pile composite foundation with raft is2.05times of rigid pile composite foundation without raft. Pile-soil load share ratio of rigid pile composite foundation with raft is0.26:0.74, and pile-soil load share ratio of rigid pile composite foundation without raft is0.12:0.88.(2) In the centrifuge test loading process of with/without raft of rigid pile composite foundation, As the distance between pile and load center increases, the value of axial force on the pile top and the value of the maximum axial force of pile decrease gradually from the center to the edge.(3) In the pile raft composite foundation, when the thickness of raft increases from0.2m to lm, the settlement value of the upper structure increases gradually; pile-soil stress ratio decreases gradually, the latter tends to be stable; load sharing ratio of pile decreases gradually and load sharing ratio of soil increases gradually, the latter tends to be stable; the value of the maximum axial force of each pile increases gradually and its size relationship is center pile> side pile> peripheral pile.(4) In the pile raft composite foundation, when the thickness of cushion increases from0.2m to0.7m, the settlement value of the upper structure increases gradually; pile-soil stress ratio decreases gradually; load sharing ratio of pile decreases gradually and load sharing ratio of soil increases gradually; the value of the maximum axial force of each pile decreases gradually and its size relationship is center pile> side pile> peripheral pile.