Relevance of interface elements in soil structure interaction analysis of three dimensional and multiscale structure on raft foundation

Effects of horizontal stresses and horizontal displacements in loaded foundation have not been adequately studied. Horizontal stresses and horizontal displacements are much affected by the nature of bonding between foundation and soil. In soil-structure interaction analysis of a structure, adopting finite element method, usage of link/interface elements between two elements of different materials is assumed to be a standard procedure. In this study two extreme cases of compatibility of horizontal displacements between raft foundation and soil elements are considered to obtain pressure settlement relations of raft foundation by developing three dimensional mathematical model and performing numerical experiments. The first case being complete slip between foundation and soil, termed as un-coupled analysis. The second case of analysis, termed as coupled analysis, adopts complete welding of joints between foundation and soil elements. The model and the computer program developed simulate responses like pressure, settlements and member end actions in structure. These two extreme states of compatibility gives insight into variation of horizontal displacements and horizontal stresses and their intricacies which lead to relevance usage of interface elements.