Computational Theory And Numerical Analysis For Consolidation And Deformation Of Composite Foundation

The settlement induced by consolidation of composite foundation is one of the important items that must be considered in design of such foundation, and its reasonable evaluation has been becoming a problem deeply concerned by engineers. However, the relevant study was rarely reported. In this dissertation, the consolidation and deformation problem of composite foundation was studied both by analytical method and by FEM. The main work includes:1. On the basis of analyzing data from several field tests, assumption was proposed for the distribution of side friction along column under rigid raft, and settlements of column and soil in the composite foundation with single column were analyzed by totally stress method. The corresponding computer program was developed at the same time.2. Based on Biot's theory, the basic equations and solution conditions were established for the consolidation problem of the composite foundation with single column considering soil-column interactions when load was applied on the top of column only or applied on the top of both column and soil, and the solution for deformations of soil and column were obtained in the forms of Laplace and Hankel transformation.3. Computer program was developed by FEM that can be used to perform consolidation and deformation analyses of composite ground for plane strain, axial symmetry and three-dimensional conditions, in which, the soil model can be linear elastic, non-linear elastic or elasto-plastic, and complicate factors such as raft, cushion et al. can be taken into consideration. Meanwhile, the program was verified by many examples.4. By assuming that distortion is coordinative and stress is in equilibrium at the interfaces of columns and soil in composite foundation and that the average consolidation degree in composite model was equal to the one in composite foundation, a three-dimensional composite model was established by effective stress analysis method. The corresponding finite element method is then developed for consolidation analysis of composite foundation. This method is advantaged by no need to distinguish column and soil and thus raises greatly the efficiency of FEM analysis, especially in consolidation analysis of composite foundation with columns group.5. The consolidation behavior of composite foundation with single column or with columns group was analyzed extensively by the computer program developed, and the mechanism that the column with low permeability can also accelerate the consolidation of soil was illustrated. Moreover, a simplified method was proposed for consolidation analysis of layered composite foundation with column of high permeability. Finally, a case study was made to show the practical application of this computer program.The work presented herein not only reveals the consolidation behavior of composite foundation, but also provides new theory and technique support for the computation of settlement induced by consolidation of composite foundation, and thus makes the computation theory for the settlement of composite foundation more perfect.