The Application Research On Calculational Model Of Plate-type Raft Foundation

Rigid pile composite ground is a new type of ground treatment.It’s composite foundation by joining the pile method make the pile soil deformation coordination, and finally through the pile and soil to take the upper loads when the natural foundation can not meet the bearing capacity and settlement requirements of the upper strcture loads. It can greatly improve the bearing capacity of the foundation soil. It is mainly used for processing viscous soil, powder soil, sand and have self-respect consolidation grain filling, etc. For the existence of Karst cave and holes area, foundation use the raft plate foundation and add the rigid pile to the foundation, should be a good structure bearing form. Through a series of engineering practice in Qingyuan karst region, the Tall Building Structure Research Institute of South China University of Technology shows that the rigid pile composite foundation-raft foundation forms can achieve construction is convenient, cost economic, safe and reliable results in these regions.Raft foundation was widely used in engineering, because its big base area can reduce the base pressure, improve the bearing capacity of foundation soil, and adjust the differential settlement. There are many methods to analyze force of the raft, such as, static titration could be used to calculate the simplified mold of force raft. Generally, all believed that the result from inverted floor method was conservative, but it was more conservative or not in circumstances was not sure. It provide that we could consider the impact of the stiffness of the upper structure when it has a better stiffness and higher, but computational analysis of the layers should not participate in more than five layers in Guangdong Province,"Building Foundation Design Code"(DBI15-31-2003).But it was also not very clear for foundation-raft foundation-the upper part of the overall structure to simulate the results of the overall finite element analysis when the upper structure was taken no more than5layers. When taking the upper structure4-layer model, the load could be added to the forth layer of the upper structure or the bottom layer (the surface of the top raft). And it was not clear that which adding loads method was better to simulate the real situation. In this paper, these problems were in doing analyzed, and then gave the corresponding results and recommendations.According to the test results of Qingyuan plate foundation soil, constitutive of the foundation soil was bilinear elastic constitutive model for the spring in this paper. And also analyzed the when foundation soil used of linear constitutive, and then do a comparative analysis between the results of both cases in the paper.