Analysis Of Dynamic Interaction Of Soil With Cave-raft Foundation-Frame Structure

The distribution of the karst area is nearly a third of our total land, where Guizhou,Yunnan and Guangxi has more. Soil cave is a more common cave form in karst region.With the rapid development of economy and urbanization process, the build structureson the foundation of the existing holes become more and more common. At present thedesign of this type of buildings is on the basis of experiences and common designmethod. The conventional methods haven’t considered the interaction between the base,foundation and the upper structure instead of considering these factors together; theresult of this method is inaccuracy. The comparison between the calculation results andengineering practice are more different when considering seismic loads. So the analysisof the dynamic interaction between upper structure, foundation and soil caves isnecessary when considering seismic loads.On the basis of domestic and foreign research results, this paper analyzed thefollowing several aspects of the dynamic interaction of upper structure-raftfoundation-soil cave under seismic loading:①The literature and material related to this topic was collected, the developmentof interaction theories was introduced briefly, and the3-D interaction model of soilcave-raft foundation-framework was established, then the used elements, boundaryconditions, damping mechanisms and interface theories were presented in detail,theselection principle and adjusting methods of seismic wave was expounded briefly.②D ynamic interaction of subsoil without cave-raft foundation-framework andsubsoil with cave-raft foundation-framework under seismic loading were compared, theresults of differences of structure vibration characteristics and the structuraldisplacement, acceleration, shear, bending moment of the two kinds of model wereanalysised in detail, and the dynamic response of he raft foundation was also compared.From the analysis results, we can see the influence of soil cave to interaction is verysignificant.③Set up six different depth of soil hole in six interaction models, analysized theinfluence of soil hole depth to the vibration characteristics and dynamic response ofthe upper structure, then compared the displacement and stress results of raftfoundation.④Set up five interaction models with different diameters of the soil hole, analysized the influence of diameters to the dynamic response of upper structure andraft foundation. Through the comparison of the results of the shear, displacement,bending moment between the raft foundation and the upper structure, the changes ofsoil hole diameters have more influences on the raft foundation than the upper structure.⑤Set up different interaction models based on the changing of the stiffness of raftfoundation, soil and frame structure, compared the displacement, internal forces ofupper structure and the displacement, stress of raft foundation results based on changesof stiffness, which provided certain theoretical basis on structural seismic designconsidering interaction with soil hole.