某超大深基坑工程围护墙变形实测与分析

某深大基坑工程采用主楼顺作、裙房逆作的总体施工方案。基于实测数据,对裙房逆作深大基坑工程的围护墙变形性状及影响因素作了深入分析。分析结果表明:首层开挖时,在东、北两侧基坑盆边预留土堤尺寸较大的条件下,盆中土方开挖所引起的墙体侧移也较为可观;围护墙平均最大侧移与开挖深度的比值为0.262%;各阶段围护墙侧移增量最大值发生位置的深度与开挖面之下的土层硬度相关,当开挖深度达15.7 m以后,因开挖面之下的土层变硬,侧移增量最大值发生的位置都在开挖面之上;基坑边角附近存在显著的空间效应,且基坑的角部空间效应随基坑角部的角度增大而减小,当基坑角部角度达110°时,基坑角部的空间效应不明显;在一定的开挖深度条件下,墙体侧移随开挖深度的增加而增大,但当开挖宽度达到一定值后,墙体侧移将不随开挖宽度的增加而增大;施工场地大门出入口处的墙体侧移受车辆动载的影响较大。

Monitoring and Analysis of Lateral Deformation of Retaining Wall of a Super-Large Deep Excavation

The excavation of a main building is performed by bottom-up construction method, and for the podium pit the top-down method is used. Based on measured data, lateral displacement of deep and big podium pit and its influencing factors are analyzed. The analysis results show that during the first layer excavation, lateral displacement of east and north wall induced by soil excavation in the middle of basin is relatively large, while the geometry of soil berms is large. The ratio between the average value of maximum lateral displacements of the diaphragm wall and the excavation depth is 0.262%. At different stages, the location of maximum lateral-deformation increment of walls is related with the soil stiffness, when the excavation depth is more than 15.7 m, the location of maximum increment is above the surface of soil excavation because of the increase of soil stiffness. The three-dimensional effect is strong at the corner of excavation, but the effect is decreasing with the angle of excavation corners, when the corner angle reaches 110°, the three-dimensional effect is not significant. Under the condition of given depth of excavation, the lateral displacement is increasing with the width of excavation, but when the width of excavation reaches the given size, lateral displacement is no more increasing with the width. The lateral displacement of wall close to the exit area is obviously affected by the vehicle dynamical load.