渗流对基坑变形及应力的影响

Influence of Seepage on Deformation and Stress of Foundation Pit

目的研究基坑的变形和应力在分步开挖的过程中受渗流的影响,分析基坑的变形和应力在考虑渗流和不考虑渗流时的差别.方法对基坑开挖卸荷与支护的过程用Fish语言编程,用FLAC3D进行数值模拟实际施工情况.在考虑渗流影响和不考虑渗流影响两种情况下,首先计算了基坑的水平位移数值解,并将坑顶位移的计算值和实测值对比,计算分析了坑底隆起和周围土体应力应变受渗流的影响.结果渗流会使基坑水平位移、竖向位移和周围土体沉降值增大,这对于基坑稳定是不利因素.渗流最明显的作用是使基坑内部和外部的水平位移都有所增大.渗流作用使基坑支护结构外侧土体竖向有效应力增大,使坑底支护结构内侧土体的竖向有效应力减小,因而增大了土体作用在支护结构上的横向作用力.结论渗流会使基坑的水平位移和坑底隆起变大,也会使周围较远的地面沉降值增大,同时会增大土体作用在支护结构上的横向作用力.

The effect of seepage on the deformation and stress of foundation during excavation is studied, and the differences of deformation and stress because of the seepage. Foundation pit excavation and supporting procedure is programmed with Fish language, then the practical scenarios is simulated by FLAC3D. Numeri- cal solution of horizontal displacement is separately solved when the seepage is considered or not. And com- parative analysis of numerical solution and measured displacement values of the pit top is made. Then, the in- fluence of seepage on the bump at the bottom of pit and on stress and strain of surrounding soil is analyzed. The results show that seepage may increase the horizontal and vertical displacement, at the same time the set- tlement of surrounding soil is increased. This is disadvantage for stability of foundation pit. The most obvious effect is increasing the horizontal displaces of the inner and out foundation pit. The horizontal force is in- creased because seepage increases vertical stress of the outer soil and decreases the stress of the inner soil. The paper realizes that influence of seepage should not be neglected. It concludes that horizontal displace- ment and bump of the bottom will be increased by seepage, as well as the settlement of the further ground and the horizontal force on the supporting structure of soil do.