邻近深基坑开挖的历史保护建筑物沉降实测分析

Analysis on settlement monitoring of historical protective buildings adjacent to deep foundation pit excavation

深基坑的开挖卸荷会引起基坑周边土体应力场和土体位移场变化,进而对邻近历史保护建筑物变形造成影响。以上海在建工程为例,对基坑不同施工阶段的邻近历史保护建筑物沉降进行监测,分析了基坑开挖对周边地层沉降、地下连续墙水平变形以及建筑物结构沉降的影响。在此基础上,也进一步分析了基坑加固措施和支撑拆除等工况对邻近建筑物沉降的影响。研究结果表明,随着基坑开挖深度的增大,邻近建筑物沉降值在逐渐增大。在第四层土开挖之前,各测点沉降值变化较缓,而随着基坑第四层土开挖,各监测点沉降值均有较大程度的增大。由于第四层土开挖施工速度较慢,基坑暴露时间较长,加大了建筑物沉降增加的风险。地下连续墙水平位移的变化可以体现邻近建筑物沉降的趋势。此外,SMW加固工法和底板浇筑施工对控制邻近建筑物的沉降有良好效果,而围护支撑的拆除也会在一定程度上增加邻近建筑物沉降,但增加幅度不会很大。研究成果可为城市深基坑施工和其他类似城市隧道、地铁等穿越工程提供一定的借鉴和参考。

The excavation of deep foundation pit may cause changes of soil stress and displacement fields,which can lead to the deformation of adjacent historical protective structures. Field monitoring is carried out during the foundation pit project in Shanghai,especially based on the deformation for historical protective buildings. The influences on ground settlements,horizontal deformation of diaphragm and building settlements during excavation are analyzed. Furthermore,the analysis of effects on the settlements of adjacent buildings because of reinforcement measures and support removing is conduct. The result shows that the settlements of adjacent buildings grow with the increasing depth of excavation. The settlement value of measuring points changes slowly before the fourth layer soil excavation,as it is in progress,the settlement value increases by a large margin. Because the excavation speed of fourth layer soil is slow and the exposure time is long,the risk of structural settlements has been enhanced. The horizontal deformation of diaphragm can reflect the deformation trend of adjacent buildings. In addition,SMW reinforcement and bottom slab concreting can control the deformation of buildings with positive effects. However,support removing can increase the settlements of buildings and the increasing degree is just a little. The research results can provide a reference for urban deep excavation and other similar projects,such as urban tunnels or subway crossing construction.