长江Ⅰ级阶地某深基坑地下水控制分析

对于地处长江I级阶地的深基坑工程而言,由于其地层软弱、水文地质条件复杂、周边建筑密集等原因,地下水的有效控制成为基坑开挖成败的关键。本文以位于湖北荆州市繁华中心城区的地下商业城某深基坑工程为例,通过理论分析和经验判断,提出采用竖向隔水帷幕+深井降水的综合方案来控制深基坑地下水问题,即在弱透水层的潜水和承压水采用在支护桩之间施打高压旋喷桩形成竖向隔水帷幕,在强透水层的承压水采用井管降水的方法来控制基坑地下水,但降水井的深度要适当。经过工程实践验证表明,弱透水层的潜水、承压水的处置措施得当,可为富水复杂环境地质条件下的深基坑工程的设计与施工提供借鉴。

Ground Water Controlling of a Deep Foundation Pit on the First Terrace of Yangtze River

For the deep foundation pit on the first terrace of Yangtze River,due to its weak formation and complex hydrologic geological conditions and surroundings,the effective control of groundwater becomes the key to the success of excavation.A deep excavation pit of an underground shopping mall in the centre of Jingzhou reaches 8.0m in depth where pore water and confined water are very rich because they are located only 700m away from the Jingjiang Dike of Yangtze River.Through theoretical analysis and experience judgments,a comprehensive solution with vertical anti-seepage curtain and dewatering is proposed to control the groundwater problems.The pore water and confined water in shallow aquitard layer are controlled through the vertical anti-seepage curtain formed by the jet grouting pile wall between the cantilever supporting piles,and the confined water in the deep high permeable aquifer is controlled through the dewatering by deep well.The depth of the dewatering well should be appropriate,otherwise the water level cannot be decreased even though there is very large pump discharge.It is shown that the proposed methods are suitable for controlling the rich pore and confined water problems in the first terrace of Yangtze River,and provide a good experience for the deep excavation pit in the complex geological conditions and surroundings.