大埋深高水压地层盾构端头加固技术数值模拟研究

Numerical Simulation of End Shield Reinforcement Technology in Deep and High Water Pressure Stratum

滇中引水龙泉倒虹吸隧洞接收端埋深高达72.3 m,地层的水土压力较大,盾构接收过程易发生涌水涌砂事故。为此,建立考虑渗流影响的盾构接收端三维模型,分析大管棚注浆和冻结法加固措施下盾构接收过程中引起的地连墙变形、地层变形和地下水渗流场变化规律,研究结果表明:盾构接收过程中,冻结法加固对限制基坑地连墙水平变形及周边土体变形的能力优于大管棚加固;大埋深盾构接收对地表沉降影响较小,可不作为重点风险源进行控制;地下水孔压场形成一个包围开挖面的低压力区,远离开挖面的孔压等值面分布较为均匀;盾构掘进至冻结加固区后地下水的渗流速度远小于大管棚加固区,对于大埋深高水压地层盾构接收工程,冻结法在抗涌泥涌砂方面明显优于大管棚加固。研究成果可为今后类似的大埋深盾构接收工程起到一定的借鉴作用。

The buried depth of the receiving end of Longquan inverted siphon tunnel is 72.3 m in Yunnan province.The water-earth pressure of the stratum is large,and the water and sand gushing accidents are prone to occur during the shield receiving process.Therefore,a three-dimensional model of the shield receiving end considering the influence of seepage was establish to analyze the deformation of the diaphragm wall,the stratum deformation and the variation of groundwater seepage field caused by shield tunnel receiving process using large pipe roof grouting and freezing method.The results show that the freezing method is superior to the large pipe roof reinforcement in the ability to limit the horizontal deformation of the diaphragm wall and the deformation of the surrounding soil in the shield receiving process.Large buried depth shield receiving has little effects on ground settlement and cannot be used as a key risk source for control.The groundwater pore pressure field forms a low pressure area surrounding the excavation surface,and the pore pressure isopleth surface far from the excavation surface is evenly distributed.The seepage velocity of groundwater after shield tunneling to the freezing reinforcement area is far less than that of the large pipe shed reinforcement area.For the shield receiving project in large buried depth and high-water pressure stratum,the freezing method is obviously better than the large pipe shed reinforcement in resisting water and sand gushing.The research results can provide reference for similar large-buried shield receiving projects in the future.