Study On Bearing Behavior Of Multi-type-pile Composite Foundation Load Of Large Tank

With the development of petroleum industry, oil tanks are used more than before, at the same time, many bad groundwork are met during the course of construction. So many of them must be treated with. How can we solve the problem with the lowest price? It is the problem that we must face with. As a kind of way of solving the problem of bad groundwork, composite foundation has two merits. The first one is that it can make piles and soil work together, and the second is that it cost low. The subject that I will study is a kind of composite foundation—multi-pile composite foundation.At the beginning of the thesis, some conclusions on composite foundation under rigid base and multi-pile composite foundation are provided. There are also a short introduction on the foundation of tanks, such as kinds of foundation used under tanks, The deformation tracks of foundation and many ways of treating with bad groundwork. And then the multi-pile composite foundation are simulated using a software Flac-3D. From the results of simulation, combined with an engineering example, we get to know some rules about the composite foundation. Here are some results :(1) No matter rigid pile or flexible pile, the largest axial stress are located at the position under top of pile.(2)There is a modulus value for rigid pile, when the modulus of rigid pile is at this value, the bearing capacity of rigid pile and flexible pile can put into good use. There are also a length for rigid pile. If length of rigid pile is larger than this value, loads sharing of rigid pile can not be improved.(3) Increasing the value of flexible pile's modulus and length can increase flexible pile's load sharing, but the effect is not very good. So the use of flexible pile is to amend soil.(4) Increasing the value of cushion 's modulus can enhance stress collection on rigid pile, the modulus of cushion under tank's base is about 250Mpa, It is larger than that of under other kind of base. So stress collection degree on rigid pile is greater .(5) Enhancing thickness of cushion can lighten stress collection on rigid pile. But the effect is limited, and it will enhance load on foundation, so we must use aproper thickness.