邻近破碎带地层斜井进正洞挑顶施工关键技术

Key Technology of Inclined Shaft into Main Tunnel Roofjacking Construction in Adjacent Fracture Zone Stratum

针对隧道斜井邻近破碎带地层造成进正洞施工段应力复杂、变形不易控制的难题,以西固隧道1号斜井与正洞交叉口处挑顶施工为研究对象,制定详细的超前支护方案、监控量测方案和变形控制方案,提出了邻近破碎带地层的双车道斜井进双洞单线隧道的挑顶施工方法,并采用有限元模拟方法评估该工法的合理性、可行性。结果表明:交叉口处邻近破碎带采用小导管超前支护、台阶法挑顶进正洞的方法可保证围岩稳定性;设置加强支护可有效解决斜井与正洞断面尺寸过大造成的围岩变形问题;交叉段拱顶围岩存在应力松弛区,该工法采用密排门式刚架增强隧道支撑,不仅能很好地拟合正洞开挖轮廓,还保障了作业安全与开挖进度。

Aiming at the problems of complex stress and difficult control of deformation in the construction section of the main tunnel caused by the stratum adjacent to the fracture zone of the tunnel inclined shaft,taking the roof⁃jacking construction at the intersection of the No.1 inclined shaft and the main tunnel of Xigu Tunnel as the research object,the detailed super⁃scheme front support,monitoring and measurement scheme and deformation control scheme are formulated,and the roof⁃jacking construction method of the double⁃lane inclined shaft into the double⁃hole single⁃line tunnel adjacent to the fracture zone stratum is proposed.The rationality and feasibility of the method are evaluated by finite element simulation method.The results show that the stability of surrounding rock can be guaranteed by using the method of small pipe advance support and step method to pick the top into the main tunnel in the adjacent fracture zone at the intersection.The setting of reinforced support can effectively solve the problem of surrounding rock deformation caused by the large section size of inclined shaft and main tunnel.There is a stress relaxation zone in the surrounding rock of the vault of the intersection section.This method uses a close⁃packed portal frame to enhance the tunnel support,which not only fits the excavation contour of the main tunnel well,but also ensures the operation safety and excavation progress.