水下隧道开挖面三维渗流场解析及涌水量预测分析

开挖面前方地层水压力及渗水量值是水下隧道工程重要参数，也是开挖面支护力设计、超前堵水加固参数设计的重要指标. 针对以往二维渗流模型分析水下隧道开挖面前方三维渗流场的局限性问题，首先，建立考虑开挖面前方渗流等势面为空间曲面的水下隧道三维渗流解析模型；其次，推导以开挖面所在平面为分界线的全部未开挖区半地层空间的水头分布函数，得出开挖面渗水量及前方地层孔隙水压力计算公式；最后，分析超前加固厚度、土体与超前加固渗透系数相对值等因素对开挖面前方水压力及渗水量的影响. 分析结果表明:与以往考虑开挖面正前方为二维渗流场的理论模型相较，三维解析模型能更好地反映开挖面前方空间渗流形态，且涌水量与水压力计算结果误差在5%以内；当掌子面前方加固范围为2倍洞室直径，超前加固区与地层相对渗透系数取值50，为安全合理的超前堵水加固参数. 

Analysis of Three-Dimensional Seepage Field and Prediction of Water Inflow in Excavation Face of Underwater Tunnels

Formation water pressure and seepage volume in front of excavation face are important parameters of underwater tunnel projects, and also key indexes for designing the support force of excavation face and advanced water blocking and reinforcement parameters. Firstly, in view of the limitation in analyzing the 3D seepage field in front of the excavation face of underwater tunnels with the previous 2D seepage model, when building the three-dimensional seepage analytical model of the underwater tunnel, the seepage equipotential surface in front of the excavation face is considered as the space surface. Secondly, with the plane of the excavation surface as the boundary, the distribution function of water head in the half stratum space of all unexcavated areas is deduced to derive the calculation formulas of water seepage at the excavation face and pore water pressure in the front formation. Finally, the influence of factors on the water pressure and seepage in front of excavation face is analyzed, such as advanced reinforcement thickness and the relative value of permeability coefficient between soil and advanced reinforcement. The results show that, compared with the previous theoretical model of 2D seepage field in front of excavation face, the 3D analytical model can better reflect the spatial seepage pattern in front of excavation face, and the error between the calculation results of water inflow and water pressure is less than 5%; when the reinforcement range in front of excavation face is twice the tunnel diameter, and the relative permeability coefficient between the advanced reinforcement area and the stratum is set as 50, which is a safe and reasonable parameter for advanced water blocking and reinforcement.