筏板基础刚度取值对其承载性状影响的数值分析

为了分析刚度大小对筏板基础承载性状的影响,采用FLAC3D有限差分软件建立了筏板基础、地基土相互作用的计算模型。在保持模型其他参数不变的前提下,通过改变筏板基础的刚度,进行了8种数值模拟计算,得到了筏板基础最大竖向应力、最大沉降量、沉降差等的变化规律;分析了上部结构群柱效应对筏板基础最大竖向应力及最大沉降量的影响。计算结果表明:当筏板基础的沉降量偏大,且不满足规范要求时,通过提高筏板基础刚度的方法以降低基础沉降量存在一个刚度上限值。当筏板基础刚度达到这个上限值时,增加基础刚度对于降低沉降量的效果不再明显。此外,如果筏板基础的不均匀沉降过大,通过增大基础刚度的方法会取得理想的效果。降低基础沉降的刚度上限值与调整不均匀沉降的刚度取值并不相等,两者之间存在一个最佳刚度取值,在工程设计时需要综合考虑其变形和经济效益。考虑群柱效应对筏板基础最大竖向应力的影响是很小的,但不考虑群柱效应的影响,将会高估筏板基础的最大沉降量。

A Numerical Analysis of the Influence of Raft Foundation Stiffness Value on Its Bearing Behavior

In order to analyze the influence of stiffness on the behavior of raft foundation, an analysis model of interaction between raft foundation and foundation soil has thus been established by using FLAC3D finite difference software. With the other parameters of the model a constant value, eight kinds of numerical simulation calculation are to be carried out by changing the rigidity of raft foundation, thus obtaining the variation rules of the maximum vertical stress, the maximum settlement and the settlement difference of raft foundation, followed by an analysis of the influence of the column group effect of superstructure on the maximum vertical stress and the maximum settlement of raft foundation. The calculation results show that when the settlement of raft foundation is too large and fails to meet the requirements of the code, there is an upper limit value of the rigidity to reduce the settlement of the foundation by increasing the rigidity of raft foundation. When the raft foundation rigidity reaches the upper limit, the effect is not obvious, however, of increasing the foundation rigidity on reducing the settlement. Moreover, if the uneven settlement of raft foundation tends to be too large, the method of increasing the foundation stiffness will achieve ideal results. The upper limit value of the rigidity to reduce the foundation settlement is not equal to the value of the rigidity to adjust the uneven settlement, with an optimal rigidity value between the two. Therefore, the deformation and economic benefits should be taken into a comprehensive consideration in the engineering design. In view of the insignificant effect of group column on the maximum vertical stress of raft foundation, and without considering the effect of group column, the maximum settlement of raft foundation will be overestimated.