为解决临江巨厚潜水含水层深基坑工程面临的地层渗透性强、涌水量大、降水难度大等问题，依托福州地铁2号线桔园洲站基坑工程，采用理论分析及三维数值模拟相结合的方法，研究不同地下连续墙深度及深层水平封底止水效果与基坑涌水量、坑外水位降深之间的关系，确定地下连续墙插入深度最优值及深层水平封底位置、厚度。工程实践表明： 1）深层水平封底实际止水效果平均达到93%以上，涌水量减少75%，有效降低了降水难度，确保了基坑工程安全顺利完工； 2）对巨厚强透水砂卵石且止水帷幕难以落底的深基坑工程，在悬挂式竖向止水帷幕基础上，设置深层水平封底止水帷幕，能有效减小坑底地层垂向渗透性，减少基坑涌水量； 3）水平封底位置需满足抗突涌要求，且上部预留一定的空间布置降水井滤管，抽排由封底渗漏至坑内的地下水。

The deep foundation pit engineering with superthick unconfined aquifer near the river always has problems such as strong permeability of stratum, large water inflow and difficulty in dewatering. The influence of different diaphragm wall depths and deep horizontal bottom sealing effect on water inflow and drawdown outside the foundation pit of Juyuanzhou Station of Fuzhou Metro Line 2 is studied by combination of theoretical analysis and threedimensional numerical simulation method; and the optimum embedded depth of diaphragm wall and the location and thickness of deep horizontal bottom sealing are determined. The engineering practice shows that: (1) The actual sealing effect of deep horizontal bottom sealing is over 93% on average and the water inflow is reduced by 75%, which effectively reduces the difficulty of dewatering and ensures the safe and smooth completion of the foundation pit project. (2) Based on the suspended water curtain for cutting off drains, the horizontal bottom sealing curtain can effectively reduce the vertical permeability of the bottom stratum and the water inflow of the foundation pit with superthick sand and pebble layer. (3) The position of horizontal bottom sealing should meet the requirements of antiinrushing, and a certain space should be reserved at the upper part so as to arrange drainage well filters to drain groundwater leaking from the bottom sealing to the pit.