葛洲坝大厦深基坑支护设计

Deep Excavation Supporting Design for Gezhouba Building

葛洲坝大厦基坑工程位于汉口市区,基坑开挖深度为16.50m～20.10m,属超深基坑,且基坑周边环境严峻,因此有必要在场地工程地质勘察基础上结合工程经验选择合理的深基坑支护方案。基坑开挖已经进入承压水含水层,必需进行降水设计,再加之桩撑支护结构在超深基坑中应用技术成熟,确定基坑围护总体方案是:放坡卸载、钻孔灌注桩+混凝土支撑、高压旋喷桩止水帷幕+坑内高压旋喷桩封底+坑内中型井点降水,坡面采用土钉挂网喷面保护。此方案的成功应用可为类似基坑工程提供一定的借鉴作用。

The Gezhouba Building is located at urban area of Hankou.The excavation depth for the building is between 16.5 and 20.1meters with a footprint area of approximately 2500 square meters.The shape of the excavation is an irregular rectangular.Due to its depth,this excavation in the urban area with strict environmental constraint belongs to a super deep category.Therefore,it is necessary to select an appropriate excavation supporting method that is most suitable for the subsurface conditions,meeting the safety requirement,having agood constructability and importantly,being cost effective.It is anticipated that the artesian layer will be encountered during the excavation;therefore,the dewatering design is also required for the construction.Since the soldier pile with rake supporting is a relatively matured technique,the general deep excavation scheme for this project is following：sloping the area to be excavated;cast-in-place reinforced concrete pile with reinforced concrete raking as supporting system.Jet grout columns as seepage cut-off curtain and as bottom artesian groundwater seal-off with point-well dewatering system in the middle of the excavated area;soil nailed wall with wire mesh and shotcrete for the slope surface protection.The construction indicates that this supporting scheme is satisfactory.