Research On Interaction Of Superstructure-Raft Foundation-Subsoil In Karst Region

The research of Superstructure-Foundation-Subsoil interaction involved in many subjects such as structural engineering and rock and soil engineering causes more and more attention. By now, analysis method for Superstructure-Foundation-Subsoil interaction used for dealing with high-rise buildings has made great progress, but seldom applied in karst area. Generally, structure designers always take the conventional design method in such complicated foundation conditions or handle it with related engineering experiences. Compare to the conventional design method separated superstructure from foundation and subsoil, Superstructure-Foundation-Subsoil interaction method is more accurated, which is considering not only the equilibrium of the force but also takes account of the equations of compatibility of displacement at the interface between structure, foundation and subsoil. It is fit the structure actual work situation and more reasonable.This paper mainly based on previous researches. A ten stories residential building located in karst region in Guiyang is taken to analyse by establishing the finite element model(FEM). It has been compared the regularity for change of stresses and deformation by using two different methods mentioned above. And uniform settlement of superstructure and raft foundation is also taken into account. The whole completed works are mainly composed of the several parts lised follows:(1) Introduces the characteristics of karst geological condition, the cause and the general rules of karst cave. In addition, the stability evaluation of karst cave and treatment of foundation methods are summarized.(2) Expounds the interaction mechanism and analysis method among Superstructure-Foundation-Subsoi, and the constitutive model of raft foundation and soil are detailed introduced in paper.(3) The elastoplastic FEM are respectively established in two different methods to simulate a ten stories residential building. Compare to the regularity for change of stresses and deformation of superstructure, raft foundation and karst cave by using two different methods mentioned above. Explore the regularity of uniform settlement of superstructure and raft foundation, and puts forward some suggestions. (4) In the end of paper, the optimization design for raft foundation has been studied. Assuming superstructure and subsoil conditions unchanged, only change the concrete strength grade and raft thickness respectly to seek a optimal scheme of economic safety for the raft foundation applied in practical engineering.