Study On Working Behaviour Of CFG Pile Composite Foundation

The pourposes of ground treatment are strength-increase of soil ground, compressive properties-decrease, settlement and differential settlement reduce of foundation.As we know,composite foundation is widely used in engineering.At present, theoretical study is far behind practice, most of the researches are based on the experiment and experience and can seldom study it with the method of numerical analysis.With the quick application of composite foundation technology in China,some problems concering its characteristics, settlement are also produced.The following questions are delt with in this paper:1. This paper presents single pile and nine CFG piles composite foundation by using of ANSYS FEM program,characteristics of co-action among pile cap-cushion-pile-earth in compostion foundation of pile cluster under vertical loading are studied with three dimensional finite element method;and load transmission characteristics and pile-soil stress ratio, settlement and their influence factors such ass/d, L/d,Ep/Es in composite foundation are systematically analysed.Furthemore,largearea group piles and single pile composite foundation which analysed by finite element analysis is expounded in this paper.2. Compared with pile foundation,settlement of composite foundation is much greater and easily to produce crack or incline in upper structure.The design method based on the theory of settlement control is more rigorous and reasonable than that based on thetheory of bearing capacity.The composite modulus Ecs =mEp +(1-m)Es, it is onlyused in particular condition .This paper gives formula of calculating composite modulus which is more reasonable and practical value of application,and combined with engineering examples to demonstrate its rationality.