混凝土垫层及水平结构混凝土收缩对围护墙变形影响的实测分析

 基于实测数据，对上海中心大厦裙房逆作超大深基坑工程的围护墙变形规律进行分析。分析结果表明，在垫层混凝土浇筑完成至梁板结构混凝土浇筑完成期间，围护墙侧移增量很小，垫层对围护墙变形具有明显的约束效应；在此期间，因作为垫层支撑点的圆形地墙受偏载作用引起较大的变形，导致测点P04墙体侧移增量较大；结合现场施工条件，对混凝土垫层约束效应的发挥进行说明。在混凝土结构养护期间，超长水平支撑梁板结构或大底板的混凝土收缩，引起围护墙侧移增量较大；且在大底板混凝土养护期间，西侧测点P23的围护墙侧移增量大于最后一次土方开挖所引起的墙体侧移增量；而短跨水平梁板结构混凝土收缩对围护墙变形影响可忽略。结合上述规律，给出相应的施工措施，以便减小基坑变形。

FIELD MEASUREMENT AND ANALYSIS FOR INFLUENCE OF CONCRETE CUSHION AND CONCRETE SHRINKAGE OF HORIZONTAL STRUCTURE ON DEFORMATION OF RETAINING WALL

Based on field measured data，the lateral deformation laws of retaining wall，which belongs to super-large deep foundation pit of Shanghai Tower podium，are analyzed. The analytical results show that，during the period from completion of cushion concrete placement to the completion of beam-slab concrete placement，the increment in lateral deformation of retaining wall is very small，indicating that the constraint effect of cushion on deformation of retaining wall is significant. However，due to the eccentric load effect，the lateral deformation of circle wall，which is the support point of cushion，is relatively large；and it leads to a large increment in lateral deformation of measuring point P04 during this period. Combining with the site construction conditions，the constraint effect of cushion concrete is explained. During the period of structure concrete curing，due to the concrete shrinkage of overlong beam-slab structure or bottom plate，the increment in lateral displacement of retaining wall is large. During the curing period of bottom plate，the increment in lateral deformation of measuring point P23 is larger than that caused by soil excavation for the last time. For the short concrete structure，the effect of concrete shrinkage on the lateral displacement of retaining wall can be neglected. Finally，based on the above laws，some suggestions are proposed to control the deformation of retaining wall effectively.