地铁车站深基坑半逆作法施工的环境变形控制分析

针对紧邻多栋7层建筑和高架地铁车站的深基坑工程，提出了地铁车站基坑半逆作施工方法并分析了环境变形控制效果.根据地铁车站的特点和周围环境控制要求，通过对比分析确定了结合临时支撑和逆作中板的半逆作施工方法，综合顺作法和逆作法的优点.对紧邻浅基础7层建筑和高架地铁车站沉降监测的结果表明：高架车站和多层建筑的沉降与差异沉降均在控制要求以内，距离基坑仅0.4 m的建筑物最大沉降小于10 mm.在逆作中板制作完成后，各测点的沉降曲线趋于平缓，即半逆作法可有效控制基坑施工后期深部开挖引起的环境变形.该方法在保证施工效率的基础上，将基坑周围变形控制在有效范围内.

Environment Deformation Caused by Semi-Top-Down Excavation of Metro Station

A semi-top-down excavation method is proposed for construction of an underground metro station, which is close to several high-rise buildings with shallow foundations and an elevated rail transit station. The efficiency of the new method to reduce the environment deformation is analyzed based on field measurements. The semi-top-down method combined the construction sequence of temporary strut and middle floor slab of the substructure during excavation, which united the advantages of both top-down method and bottom-up method. The settlement observation of the high-rise building and elevated rail transit station show that both the settlements and the differential settlement are within control, and the maximum settlement of the buildings, which is only 0.4 m far from the diaphragm wall, is less than 10 mm. After the middle slab is constructed, the increase of settlements trend to be mild, which means that the semi-top-down method has a good effect on controlling the surrounding deformation caused by excavation. Therefore, the new method can ensure the efficiency of deep excavation and reduce the environment-deformation.