岩溶弱发育地层隧道衬砌水压规律及结构安全性研究

Study on Water Pressure Law and Structural Safety of Tunnel Lining in Karst Weakly Developed Strata

当地层岩溶弱发育时,地表水下渗速度相对较慢。这种条件下,隧道常规防排水方案是否能够有效排导地下水,降低衬砌背后水压,还需要进一步研究。以重庆市某岩溶弱发育高铁隧道工程为依托,设计衬砌拱顶水头高度为10,15,20 m及30 m四种工况,采用三维数值模拟方法对常规隧道防排水方案条件下岩溶隧道衬砌水压分布规律及结构安全性进行研究。研究结果表明:(1)正常排水条件下,隧道衬砌水压折减率拱顶比仰拱高,且随着水头高度增加,折减率也随之减小;(2)在水压和围岩压力共同作用下,初始水头高度为10 m和15 m时,衬砌结构能够满足安全性要求,当初始水头超过20 m时,衬砌结构不能满足安全要求;(3)当常规隧道防排水方案用于岩溶弱发育段隧道时,需要对仰拱的排水方案进行改进或优化,以达到结构安全的要求。

When karst is in weak development,the infiltration rate of surface water is relatively slow.Further research is needed in terms of whether the tunnels conventional anti-drainage scheme can effectively drain groundwater and reduce hydraulic behind the lining.Based on a weakly developed karst tunnel in Chongqing,the design lining vault head height is 10 m,15 m,20 m and 30 m for four working conditions.The threedimensional numerical simulation method was used to study the water pressure distribution law and structural safety of karst tunnel lining under the condition of conventional tunnel waterproof and drainage scheme.The results show:(1)Under normal drainage conditions,the water pressure reduction rate of tunnel lining vault is higher than that of inverted arch,and the discount rate decreases as the head height increases.(2)Under the combined action of hydraulic and surrounding rock pressure,the lining structure can meet safety requirements when the initial water head heights are 10 m and 15 m.When the initial water head exceeds 20 m,the lining structure cannot meet the safety requirements.(3)When conventional anti-drainage schemes are used in tunnels with weak karst development,it is necessary to optimize the drainage scheme of the inverted arch.