公路隧道二次衬砌厚度的优化

应用工程类比法对榆树沟隧道二次衬砌厚度进行了优化设计, 选取了Ⅱ类围岩浅埋、Ⅲ类围岩及Ⅳ类围岩三种不同的复合式衬砌结构类型, 对隧道开挖后围岩和初期支护的力学状态采用FLAC软件进行了模拟计算, 对二次衬砌的力学状态采用ANSYS软件进行了分析。结果表明三种衬砌结构类型的二次衬砌内力都较小, 最大轴力为165 kN, 最大弯矩为-15.97 kN.m, 且都发生在Ⅱ类浅埋断面, 二次衬砌的安全系数较大; 衬砌周边位移最大的是Ⅱ类围岩浅埋, 其洞周位移最大值(18 mm) 发生在拱脚处, 边墙围岩收敛较小, 且围岩越好, 周边位移越小; 现场监控量测的净空收敛数值均远小于允许收敛值, 二次衬砌接触压力的量测值均远小于规范计算值。可见, 二次衬砌工作状态良好, 安全储备较大, 减薄二次衬砌厚度的隧道结构是安全的。

Secondary lining thickness optimization of road tunnel

Engineering analog method was adopted to take the secondary lining thickness optimum design of Yushugou tunnel, shallow-buried Ⅱ class rock, Ⅲ class rock and Ⅳ class rock, which are three different kinds of composite lining structure types, were selected, the software FLAC was used to take analog computation on the surrounding rock and primary support's strained condition after the tunnel was excavated, then the software ANSYS was used to take analytical computation on the strained condition of the secondary lining.Computation result indicates that the secondary lining's internal forces of three different kinds of lining structure types are less, the maximal stress is 165 kN, the maximal bending moment is-15.97 kN·m, and both of them happen in the section of shallow-buried Ⅱ class rock, the safety factor of the secondary lining is large; the maximal circumjacent displacement of the lining occurs in the situation of shallow buried Ⅱ class rock, the maximal displacement (18 mm) of the surrounding portal happens in spring, the surrounding rock displacement in side wall has a less convergence, the better the surrounding rock is, the smaller the circumjacent displacement is.The result of monitoring measurement indicates that the convergence of tunnel inner perimeter is far smaller than allowed convergence, the measured pressure values of contact surface in the secondary lining are smaller than the calculated values in specification, the secondary lining has good work condition and its safe provision is enough, so tunnel structure is safe when reducing the thickness of secondary lining.