上海地区土层中广泛分布②3层灰色砂质粉土,该土层局部夹大量粉砂,施工时易产生流砂、管涌等现象。本文结合上海地铁工程施工实际,详细介绍和分析了盾构进、出洞过程中采用真空井点降水止水的方法,可为类似工程提供参考。 Widely distributed in the soil layer in Shanghai ② 3-layer gray sandy silt, which is partly sandwiched with a large amount of silt, is prone to produce sand and piping during construction. Combined with the actual construction of Shanghai Metro, this paper introduces and analyzes in detail the method of using point-dewatering and sealing of vacuum wells in the process of shield tunneling and hole-closing, which can provide references for similar projects.