软土地区基坑分区开挖参数分析

Parameter analysis of zoned excavation in soft soil area

在敏感环境下施工时,为减小基坑开挖对临近结构的影响,常将深大基坑用分隔墙分割成若干个小基坑。以上海软土地区某工程为背景,借助数值计算,分析深大基坑分区开挖时分区宽度、分区开挖次序和分隔墙插入比对临近被保护结构一侧地下连续墙和墙后土体变形的影响。研究结果表明:当先远后近(远近相对于被保护结构而言)方式开挖,分区宽度等于基坑开挖深度时,分区开挖的作用效果最好,此时墙体水平位移和墙后地表沉降比未分区时分别小39%和41%;当先近后远的方式开挖时,分隔墙离基坑边缘越近,分区开挖的作用效果越明显;在同等分区宽度下,先远后近开挖所引起的墙体变形和墙后地表沉降比先近后远开挖的低;分隔墙的插入比对基坑围护墙位移和墙后土体沉降影响比较小。

In order to reduce the impact of deep excavation on adjacent structure, the deep and large excavation was usually divided into several small ones by cross walls during excavating in sensitive environment. Based on a deep and large excavation in Shanghai soft clay, the influence of partition width, excavation sequence and insertion ratio of the cross wall on the deformations of diaphragm wall and behind soils nearby the protected structures were studied through a series of numerical analysis. The results show that the most ideal partition width equals the final excavation depth for the far-to-near (far or near is relative to the protected structure) excavation. In this case, the horizontal displacement of the diaphragm wall and the surface settlement behind the wall decrease by 39% and 41% respectively in comparison with the unzoned excavation. For the near-to-far excavation, narrow partition width is more beneficial than wide partition width during zoned excavation. Under the same partition width, the deformation of the diaphragm wall and the surface settlement behind the wall caused by the far-to-near excavation is less than that of the near-to-far excavation. The insertion ratio of the cross wall only has a comparatively slight impact on the diaphragm walls deformations and behind soils settlements.