土质地层公路隧道大断面快速施工技术研究

随着交通工程建设的快速发展，公路长大隧道越来越多，常规施工方法效率较低，无法满足工期要求，这对公路隧道快速施工技术提出了新的挑战。以东天山特长公路隧道为背景，提出土质地层隧道大断面开挖工法，通过力学分析及现场对比试验，分析论证了该工法的可行性。结果表明：土质隧道大断面开挖时，采用超长小导管能够减少上部围岩压力对掌子面滑动土体的荷载作用，预留核心土则能够为掌子面滑动土体提供支撑反力，通过这2种控制措施能够实现土质围岩隧道掌子面稳定；相比台阶法，大断面开挖时围岩应力释放速率较快，变形快速发展，拱架和喷混凝土受力快速增长，支护封闭成环后可得到有效控制，但需进一步提高初期支护早期承载性能，即提高喷混凝土早期强度；采用大断面工法能够提升机械作业空间，简化工序，实现多组设备同时作业，相比两台阶施工，隧道施工效率提升约22%。综合评价，土质地层隧道采用大断面快速施工工法能够实现掌子面稳定，支护结构安全，且相比台阶法施工效率可得到显著提高。

Research on Highway Tunnel Rapid Construction Technology with Large-section Excavation in Soil Layer

With the rapid developments in traffic engineering construction and the increasing number of highway tunnels, the conventional tunnel construction method with low efficiency cannot satisfy the time limits, which poses a new challenge to highway tunnel rapid construction technology. Based on the Mt. Dongtian Tunnel, a tunnel large-section excavation method of soil strata was proposed, the feasibility of which was proven by a mechanical analysis and field comparative test. The results demonstrate that an ultra-long small pipe can reduce the load of the surrounding rock pressure on the slipping soil of the tunnel face, whereas core soil can provide a supporting force to the slipping soil of the tunnel face. By using these two control measures, the tunnel face can be stabilized in the soil layer. Compared to the bench excavation method, the surrounding rock pressure release rate of large-section excavation is much faster, the deformation rate is rapid, and the stresses of the steel arch and shotcrete are quickly increased, all of which can be controlled until the invert is completed. Therefore, it is necessary to improve the early bearing capacity of the initial lining further by improving the early strength of shotcrete. The large-section excavation method can provide more space for working machines and the construction processes are simple; thus, it can realize the simultaneous operation of multiple machines in the tunnel. Compared to the bench excavation method, the efficiency of the large-section excavation method is increased by approximately 22%. According to the comprehensive evaluation, the large-section excavation method can provide tunnel face stability, safe initial lining, and higher construction efficiency than the bench excavation method.