基于流固耦合的高水压隧道支护结构研究

Study on High Water Pressure on Tunnel Supporting Structure Based on Fluid-solid Coupling

高水压是山岭隧道建设的重要难题之一,抗水压衬砌是隧道穿越这些区段的常用措施,其衬砌结构断面厚度远大于标准断面。衬砌厚度过大施工相对不便,施工质量不能保证,且不能及时分担水压。针对广西某隧道高水压段,采用双层初期支护和二次衬砌组成的支护结构承受高水压,减小二次衬砌厚度。为了分析双层初期支护的效果与获得基于双层初期支护的支护结构参数,利用有限差分法研究了不同防渗等级的单层与双层初期支护、不同注浆范围及不同二次衬砌厚度对围岩的变形影响和对支护结构的力学状态影响。结果表明:在相同支护体系中,喷射混凝土的不同防渗等级对围岩变形、支护应力影响不大;初期支护的防渗等级相同时,相比于单层初期支护,双层初期支护体系使围岩变形、喷射混凝土应力、二次衬砌的轴力与弯矩均减小40%以上;当拱顶以上水头为90 m且采用防渗等级为P8的双层初期支护时,径向注浆能够有效减小支护应力。当径向注浆范围超过4 m后,注浆对减小支护结构受力的效果不明显;采用双层初期支护体系,注浆范围为4 m时,二次衬砌的厚度设计为40 cm就能保障支护结构处于安全状态;径向注浆条件下,采用双层初期支护+二次衬砌的支护体系能够有效保障隧道高水压段的安全。

High water pressure is one of the most important problems in the construction of mountain tunnels.Anti-hydraulic pressure lining is usually used when the tunnel face this problem.The thickness of the lining in high water pressure part is much larger than the standard lining thickness.If the lining thickness is too large,the construction is relatively inconvenient,the construction quality cannot be guaranteed,and the water pressure cannot be shared in time.For the high water pressure section of a tunnel in Guangxi,the high water pressure is born and the thickness of the secondary lining is reduced by adopting a supporting structure composed of double-layer primary support and secondary lining.In order to analyse the effect of double-layer primary support and obtain the support structure parameters based on the double-layer primary support,The influences of single-layer and double-layer primary supporting with different seepage prevention grades,grouting ranges and secondary lining thicknesses on the deformation of surrounding rock and the mechanical state of support structure are investigated by using finite difference method.The result shows that(1)Different seepage prevention grades of shotcrete has little influence on surrounding rock deformation and supporting stress in the same support system.(2)When the seepage prevention grade of shotcrete is same,the double-layer primary support can reduce the deformation of surrounding rock,stress of shotcrete,axial force and bending moment of secondary lining by 40%at least than single-layer primary support.(3)When the 90 m water head above the vault and the double-layer primary support with seepage prevention grade of P8 is adopted,the radial grouting can effectively reduce the supporting stress.When the radial grouting range exceeds 4 m,the grouting has little effect on reducing the stress of the supporting structure.(4)When the double-layer primary support system is adopted and the grouting range is 4 m,the secondary lining with the thickness of 40 cm can ensure the safety of the supporting structure.(5)Under the condition of radial grouting,the support system of double-layer primary support and secondary lining can effectively guarantee the safety of high water pressure part of tunnel.