Stress Analysis And Settlement Calculation Of Pile Raft Foundation Based On Mindlin Stress Solution

At the present time, pile raft foundation has been abroad used in projects. But the state of pile raft foundation under the loads are very complex. There hasn't been the accurate description to describe the reaction of the subsoil in different case yet. In order to accurately analyze the additional stress and the settlement under the foundation, we need take into account the interaction of the structure, the pile raft foundation and the subsoil.When analyzing the additional stress and the settlement under the foundation, the model of pile foundation is developed based on the above theory and method. The pile is simplified as a nonlinear elastic spring. The raft is simulated by the 4-node degenerated element. Single stiffness is presented through the single pile's settlement, and the load of the top of pile is computed by circulating many times, so it can avoid man-made rectification. When presenting the single stiffness, the author not only think over the effect of the foundation, but also think over the effect of the structure.Under taking into account the raft and the structure's effect in group foundation, the author has edited a set of software, based on this method, to calculate stresses and settlements of pile foundation. This software has visual interface. So it is very convenient to use. When calculating the additional stress and the settlement, the paper are based on Geddes' assumption and the Mindlin stress solution. After calculating, the software can give the group foundation's settlement contour, additional stress contour, the value of every point's settlement and additional stress, and the change curve of additional stress as the depth increasing. Using the software, the reaction of pile raft foundation has been analyzed, and the main influencing factors of Mindlin stress solution influence the settlement has been discussed. Contrasting the settlement and the additional stress by considering the raft or not.At the end of the paper, the application of the method is introduced on a project, and compare the group foundation's settlement using Mindlin stress solution with the other methods which prescribed by building code. So the reader will have a further grasp in those methods, especially in Mindlin stress solution. It is shown that, compared with others, the design method is close to the practical situation.