Research On Macroscopic Constitutive Of Rigid-pile Composite Foundation In Karst Region And Its Effects On Internal Force Of Raft

Geological structures are so complex in Karst Area that lots of engineering hiddendangers for construction.With the rapid development of national economy, the land resourcesare becoming more and more deficient. You might even say:an inch of land, an inch of gold.To meet the social housing needs, the land use of Karst Area is imperative. Pre-construction,we must deal with karst caves. At present, we mainly through bored piles grouting cementmortar or punching pile throughout karst caves. The surface of the karst undulates so greatlyas well as Karen and fracture develops that broken pile and inclined pile happen frequently orKarst cave linking to each other that they can’t be fill up, which lead to the unpredictability oftime limit, bring direct or indirect economic loss to the project.However,the rigid pilecomposite foundation—raft foundation can overcome the above difficulties so that they havebeen used widely in the past years.Research on composite foundation starts late in our country, especially rigid pilecomposite foundation. The theory of the composite foundation is far from meet the needs ofengineering practice. With regard to the constitutive relation between bearing capacity andsettlement of composite foundation research is scanty especially, which cause the uncertaintyof engineering design and then hinder the development of composite foundation.Through the mathematical statistics analysis of44plate loading tests of single pilecomposite foundation under four types of typical geological conditions, we abstract thebilinear and four broken-line spring constitutive models, which are based on the Winklerfoundation model. Then we use interactive analysis method to do the parameters sensitivityanalysis through a practical engineering and find the suitable constitutive curve which is usedto guide the engineering design. The analysis conclusions can be reference in design ofcomposite foundation under similar geological conditions.In view of the raft Internal forces are controlled by what kind of working conditionproblem, this article ananlysis144models’ share ratio ofN maxvarious combinations forvertical members under different seismic intensity, different wind presssure, and different ground roughness by means of PKPM. Analysis results can guide the raft design later.In order to reduce raft internal force mutations which caused by differential settlementproblem between the soil and rock on the same site, this article put forward using EPS boardfor settlement control. Based on the press laboratory experiment data’s and stress-strainrelationships, we fitting out the three broken-line constitutive model which can be convenientused for engineering application. Through numerical analysis, we know that the EPS plankcan coordinate deformation well and reduce raft internal force mutations, which can meet theengineering requirements.