基于Geddes应力解的桩筏基础沉降计算

桩基础沉降计算理论在国内应用较多的是Geddes应力法,目前在应用Geddes解计算桩基础沉降时,一般不考虑筏板刚度的影响,假定所有桩均分上部荷载,理论上存在缺陷。为了使桩筏基础的沉降计算更加合理,本文将薄板理论与Geddes解结合在一起,提出分析桩筏基础的新方法。该方法采用Kirchhoff薄板理论模拟基础底板,土被当成各向同性弹性半空间体,桩与桩之间以及桩土之间的相互作用通过Geddes解实现,采用有限单元法计算出每根桩分担的荷载,据此桩顶荷载,根据Geddes解计算桩基沉降。本方法解决了桩基沉降计算理论上的不足,使计算原理和计算结果更加合理。同时,在有限元计算中,采用对角阵近似代替群桩的满秩刚度矩阵,使计算时间大大缩短,能够分析较大规模的桩筏基础。

Settlement Calculation of the Piled Raft Foundations Based on Geddes Solution

When Geddes Solution is applied to the settlement calculating of piled raft foundations , the rigidity of the raft cannot be effectively considered in the Geddes solution, which assumes all the piles bear equal load, such is a theoretical imperfection. In this paper, a new method is presented, which combines the finite element method (FEM) together with the Geddes solution. Kirchhoff thin plate theory is used to model the raft, the soil is assumed to be an isotropic elastic half-space, Geddes solution is used to simulate the interaction between the piles and pile-soil, FEM is used to calculate the loads carried by every pile, then the settlement can be calculated by Geddes solution. The new method can overcome the imperfection of Geddes solution and make the result more reasonable. Simultaneously , the diagonally matrix is used to replace the entire matrix of piles group, then the calculating time is reduced, this make it more possible that the new method presented here to be applied to large-scale piled raft foundations.