深汕西改扩建工程超大跨公路隧道设计与实践

Design and Practice of Super-Large Span Tunnel for Shenzhen-Shantou Western Expressway Extension Project

为解决超大跨公路隧道在设计施工过程中普遍存在的工法选择、支护参数确定等技术难题,基于广东省深汕西高速改扩建项目双洞8车道超大跨公路隧道建设实例,通过调研、工程类比、模拟计算等方法,进行超大跨公路隧道在施工工法、支护参数、“一洞九线”大型机械化工装配置以及相关优化设计等方面的研究,并通过监控量测对设计方案进行验证。结果表明:1)现行规范中2、3车道隧道的设计方法仍基本适用于4车道隧道。2)CD法适用于深埋强风化层,且拱顶强风化层厚度不小于1倍洞身开挖宽度;三台阶法适用于深埋中风化层,且拱顶中风化层厚度不小于1倍洞身开挖宽度。3)采用?51超前中管棚、掌子面玻璃纤维锚、涨壳式预应力锚杆以及C30早高强喷射混凝土后,在Ⅳ级围岩中进行机械化施工具有较高的可行性。4)在前述超前预加固以及支护优化的前提下,当仰拱与掌子面的距离优化至106 m(CD法)、118 m(三台阶法),二次衬砌与掌子面的距离优化至160 m(CD法)、190 m(三台阶法),机械化施工可达到安全、高效的预期。

To rationally select construction methods and support parameters in the design and construction process of super-large span highway tunnels,a case study is conducted on a double-hole eight-lane super-large span highway tunnel of the Shenzhen-Shantou western expressway extension project in Guangdong province,China.The investigation,engineering analogies,and simulation calculations are employed to examine the construction method,supporting parameters,"one-hole nine-line"large-scale mechanized tooling configuration,and related optimization design of superlarge span highway tunnel.Furthermore,the design scheme is validated through monitoring and measuring.The results reveal the following:(1)The design methods for two-and three-lane tunnels in the current specifications are still basically applicable to four-lane tunnels.(2)The center-diaphragm(CD)method is suitable for deep and stronglyweathered strata with a thickness in the arch no less than 1 times the excavation width of the tunnel;whereas the threebench method is suitable for deep and moderately-weathered strata with a thickness in the arch no less than 1 times the excavation width of the tunnel.(3)The mechanized construction method can be applied in GradeⅣsurrounding rock after implementingϕ51 advance middle pipe roof,glass fiber anchor,expanded shell prestressed anchor,and C30 early high-strength shotcrete.(4)Under the premise of advance pre-reinforcement and support optimization mentioned above,the mechanized construction method is applicable when the distance between the invert and the tunnel face is optimized to 106 m(CD method)or 118 m(three-bench method),and the distance between the secondary lining and the tunnel face is optimized to 160 m (CD method) or 190 m (three-bench method).