基于地层加固的海底隧道极限顶板厚度确定方法

海底隧道顶板厚度直接关系到海底隧道工程的经济性和安全性，如何在地层加固条件下确定顶板厚度是海底隧道穿越不良地质体施工的关键问题之一。针对该问题，文章首先对国内外典型海底隧道突水事故进行分析，进一步阐明“极限顶板厚度”的物理意义，结合合理注浆加固参数与顶板厚度相互制约的特点提出极限顶板厚度确定方法，其核心为合理注浆加固参数和塑性区范围的确定方法；进而建立考虑渗流作用和超前加固的海底隧道围岩力学分析模型，基于对塑性区发展模式的分析，对海底隧道围岩进行弹塑性解析，在此基础上对加固参数的敏感性进行分析，以围岩位移最小和渗水量最低为目标，基于分层排序法提出海底隧道超前加固参数多目标优化方法，从而可确定最优极限顶板厚度值。将该方法应用于青岛胶州湾海底隧道工程，验证其合理性和可行性，可为海底隧道的规划选线和安全施工提供理论依据。

Determination method of limited rock cover for subsea tunnel#br# based on ground reinforcement

 Rock cover for subsea tunnel has direct influence on the economy and safety of tunnel project, so how to determine the rock cover is one of the key problem of tunnelling crossing the unfavorable geological bodies. Aiming at this problem, typical subsea tunnel water inrush accidents worldwide are first analyzed, furthermore the physical significance of “limited rock cover” are clarified. Combining the mutual restriction characteristic of reasonable grouting reinforcement parameters and the rock cover, the determination method of limited rock cover is proposed, in which the core is determination of the thickness of plastic zone and reasonable grouting reinforcement. The mechanical model of subsea tunnel surrounding rock considering advanced reinforcement and seepage effect is proposed. Based on the possible distribution of plastic zone(s), surrounding rock are theoretically analyzed. On the basis of the given calculation formulas, the sensitivities of reinforcement parameters are analysed. Taking the minimum surrounding rock displacement and the lowest seepage volume as the targets, the reasonable determination method of solving the reinforcement ring parametric multi-objective optimization problem of subsea tunnel is proposed based on the stratified sequencing method to determine the optimal limited rock cover. The method has been applied in Jiaozhou Bay subsea tunnel, whose rationality and feasibility are verified, providing the theoretical basis for the planning and safe construction of subsea tunnels.