Macro Constitutive Study And Finite Element Analysis Of Composite Foundation In Karst Region

A large number of high-rise buildings have sprung up in karst region, which requirehigher bearing capacity of base ground. Because of the karst development, hidden dangerarises in engineering, such as karst ground subsidence, subsidence of pile-tip bedrock and soon. What’s more, lots of problems occur in foundation treatment. To avoid the adversegeological conditions and give full play to the bearing capacity of foundation, a combinationof raft foundation and composite foundation is gradually being extended.This paper design precast-pile composite ground of one high-rise building in Qingyuancity. In the plate loading test of single-pile composite ground, the settlement of pressure plateis monitored, as well as pile-soil stresses. Therefore, deformation capacity of rigid pilecomposite foundation and pile-soil interaction has been studied, which prove the feasibilityand effectiveness of foundation treatment.According to the test results and engineering experience, this paper put forward abilinear spring macro constitutive model. In order to study the law of internal force anddeformation, the software SAP2000was used to analyze the interaction of superstructure-raftfoundation-composite ground. The analysis on parameter sensitivity of macro constitutivemodel ensures the safety of its engineering applications.With the rationality of model, numerical simulation analysis of the plate loading test byABAQUS was compared with the test result to analysis the pile-soil interaction and loadtransfer mechanism. According to compressibility of bearing course at pile end, the influenceof the thickness of cushion on deformation characteristics of composite foundation wasevaluated, while suggestion of foundation treatment was given.The achievements of size effect at home and abroad were summarized in this paper. Thesize effect of rigid-pile composite foundation was studied, comparing with the model ofequivalent reinforcement soil layer. According to national code, some engineering advice wasgiven to make sure that it’s safe enough to adopt the test result of single-pile compositeground in the design of raft foundation in large size.