远场静水压力作用下深埋隧道双层叠合衬砌合理组合形式及力学变形特性研究

Research on Reasonable Combination Forms and Mechanical Deformation Characteristics of Double-layer Superimposed Lining in Deep-buried Tunnels under the Action of Far-field Hydrostatic Pressure

针对深埋长大隧道传统复合式衬砌结构在遭遇高水头地下水威胁的问题,研究了双层叠合衬砌方案,该方案采用“结构一分为二、两道防水设防”的设计理念,既能克服大体积混凝土施工的困难,又可以解决二次衬砌结构渗漏水的弊病。文章以青岛地铁1号线过海隧道为工程依托,借助ANSYS有限元计算软件,对双层叠合衬砌的合理组合形式及力学变形特性进行了分析,结果表明:叠合衬砌内力分配与内外层结构刚度比有关,刚度越大则内力越大,当内外层结构刚度比为0.716时,t_(A)=0.95 m和t_(B)=0.85 m为最优叠合衬砌厚度组合;隧道结构各控制截面的风险排序为仰拱>拱脚>拱顶;叠合衬砌在外水压力作用下,内外层衬砌变形是相互协调的,仰拱结构变形对刚度比、外水压力量值均较拱顶、侧墙更为敏感;叠合衬砌组合形式是受结构承载力控制而不是受变形控制;最优叠合衬砌组合在外水压力小于1.2 MPa时,结构安全性同样受承载力控制。

In regards to the threats to traditional composite lining structure of deep-buried long tunnels caused by groundwater with high water head,this paper studies a double-layer superimposed lining scheme,which adopts the design concept of"dividing the lining structure into two parts and installing two water-proof layers",to not only overcome the construction difficulties of mass concrete but also address the leakage issue of secondary lining struc⁃ture.This paper takes the sea-crossing tunnel project of Qingdao metro line 1 as the engineering basis and analyzes the reasonable combination forms and mechanical deformation characteristics of the double-layer superimposed lin⁃ing through the finite element calculation software ANSYS.The results show that the internal force distribution of the superimposed lining is related to the structural stiffness ratio of the inner and outer lining layers;the greater the stiffness ratio is,the greater the internal force will be,and when the structural stiffness ratio of the inner and outer lining layers is 0.716,the optimal combination of the superimposed lining thickness is t_(A)=0.95 m and t_(B)=0.85 m;the risk ranking of each control section of the tunnel structure is inverted arch>arch foot>vault;under the action of ex⁃ternal water pressure on the superimposed lining,the deformation of inner and outer lining layers is coordinated with each other,while the deformation of the inverted arch structure is more sensitive to the stiffness ratio and the exter⁃nal water pressure value than that of the vault and sidewalls;the combination form of the superimposed lining is con⁃trolled by the structural load-bearing capacity rather than by the deformation;the structural safety of the optimal su⁃perimposed lining combination is also controlled by the bearing capacity when the external water pressure is lower than 1.2 MPa.