软土地区临江深大基坑工程地下水综合控制技术实践

Practice of multi-methods of groundwater control technology in deep and large excavations adjacent to rivers in soft soil area

软土地区临江基坑设计施工中,地下水控制是重中之重。某水文地质条件复杂的上海临江深大基坑工程实践,在上海软土地区临江基坑中首次采用深达44.5 m超深双轮铣深搅(SMC)水泥土搅拌墙落底止水帷幕。基于工程实施效果,总结形成了一套超深双轮铣深搅(SMC)工艺水泥土搅拌墙止水帷幕+现场抽水试验+承压水数值分析+信息化设计施工等多重手段结合的地下水综合控制技术。设计分析和监测数据表明,设计采取的“大坑化小坑”分区设计等控制基坑变形措施,有利于确保止水帷幕的连续封闭且减小坑外不均匀沉降。钻孔取芯检验和现场试抽水试验表明,超深SMC止水帷幕芯样强度和渗透系数满足设计要求。实施效果证明,本项目采用的多重手段结合地下水控制措施效果良好,可为临江基坑落底式止水帷幕相关工程实践提供技术参考。

In the design and construction of excavations adjacent to rivers in soft soil area, groundwater control is the top priority. In the practice of a deep and large excavation near the river in Shanghai with complex hydrogeological conditions,it is the first time in Shanghai that super deep SMC(Soil Mixing Cutter) constant thickness cement-soil wall as long as 44.5m was used as waterproof curtain. Based on the practice, multi-methods of ground-water control technology was proposed,including super deep constant thickness cement-soil wall constructed by Soil Mixing Cutter(SMC) method, groundwater pumping test on-site, numerical analysis of confined water and information-oriented design & construction. The design analysis and monitoring data show that the "dividing large excavations into small ones" zoning design and other control measures could efficiently control the deformation of the excavation, meanwhile ensure the continuous closure of the deep waterproof curtain and reduce the uneven settlement outside. Borehole core inspection and on-site pumping test proved that the strength and permeability coefficient of the core sample of the super deep SMC waterproof curtain well meet the design requirements. The monitoring data showed that the multi-methods of ground-water control technology adopted in this project performed well, effectively controlled the impact of excavation and dewatering on the surrounding environment, which could provide technical reference for the design consultation of related projects adjacent to rivers.