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在上海软土地质条件下,深逾7 m的基坑大多采用排桩+钢筋混凝土水平内支撑进行支护,但大量的水平内支撑施工不但增加了工程量,而且制约了出土速度。因此,排桩+中心底板钢抛撑技术在深6~8 m的基坑中逐渐被推广应用。但中心底板斜抛撑支护施工又使挖土分为2个阶段,也给基坑质量与安全带来一定的隐患。基于此,以某深8.45 m基坑为例,介绍一种双排工法桩+超前植入钢斜撑的新型支护体系。即超前注浆端承钢斜撑在深基坑工程挖土施工前打入,为门架围护体系提供可靠支撑,避免了地下结构与换撑、内支撑拆除的交叉作业,施工速度快、周期短。该体系目前在实际应用中效果明显,取得了不错的社会及经济效益。
Under Shanghai soft soil geological conditions, deep foundation pits more than 7 m in depth are supported by the horizontal internal supports of piles and reinforced concrete. However, a large number of horizontal internal supports not only increase the engineering volume but also restrict the speed of excavation. Therefore, the row of piles + central floor steel throwing technology in deep 6 ~ 8 m of the pit is gradually being widely used. However, the center slab slashing bracing support construction in turn make excavation is divided into two stages, but also to the pit quality and safety bring some hidden dangers. Based on this, taking a deep foundation pit of 8.45 m as an example, a new type of supporting system with double-row working method + pre-implantation steel bracing is introduced. That is, the advanced grouting end bearing steel bracing penetrates deep into deep foundation pit excavation before construction, providing reliable support for the gantry enclosure system and avoiding the cross-operation of underground structure replacement and internal support dismantlement, the construction speed is fast, Short cycle. The system is effective in practical application and has achieved good social and economic benefits.