长江漫滩地区深大基坑开挖工程半逆作半顺作法研究

针对长江漫滩高承压水地基，以南京市某工字型地下6层地铁换乘站基坑为依托工程，采用FLAC3D三维有限差分软件，分别对半顺作半逆作开挖法和明挖顺作法进行数值模拟，分析了基坑开挖及降水的应力渗流耦合作用对周围地表沉降、连续墙侧移和支撑轴力的影响。结果表明：1)长江漫滩高承压水地基深基坑开挖工程，地表沉降值和连续墙变形值均较大；2)工字型深基坑开挖工程，地表沉降、连续墙侧移最大值出现在上下横边中点处；3)半顺作半逆作法的地表沉降、连续墙侧移、横向支撑轴力值均小于明挖顺作法，更有利于控制基坑侧壁变形，降低基坑开挖风险。

A study on the semi-inverse and semi-normal practice of deep and large foundation pit excavation in Yangtze River floodplain area

To study the deep foundation pit excavation of the high confined water foundation in the Yangtze River floodplain area, a Nanjing I-shaped 6 floor underground metro transfer station foundation pit excavation was selected as research object. Using finite difference software FLAC3D, numerical simulation on semi-normal and semi-reversed construction method and the cut and follow method was carried out separately, and the effects of the coupling action of the foundation pit excavation and stress seepage of precipitation on the surrounding surface settlement, lateral displacement of diaphragm wall and supporting axial force were analyzed. The findings show that: 1) in the deep foundation pit excavation project of high confined water foundation of the Yangtze River floodplain, both the surface settlement value and the continuous wall deformation value are large; 2) in the excavation of I-shaped deep foundation pit, the maximum value of surface settlement and continuous lateral displacement of wall occurs at the midpoint of the upper and lower transverse edges; 3) the surface settlement, lateral displacement of continuous wall and axial force value of transverse support in the semi-normal and semi-reversed construction method are all lower than that in the cut and follow method, conducive to controlling the lateral wall deformation of foundation pit and reducing the risk of foundation pit excavation.