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关角隧道是西(宁)格(尔木)二线的控制性工程,在隧道入口处存在长约450m的砂层,施工难度较大。由于在3台阶施工中出现了冒顶事故,故提出了4台阶施工的设想,并利用三维数值计算模拟了4台阶开挖支护过程,揭示了隧道的空间变形、地表沉降和初支受力特征。通过与3台阶施工模拟结果对比证实了4台阶方案的优越性;现场施工和变形量测结果表明,采用大拱脚断面形式和超短四台阶施工方案,施作长大水平超前管棚、设置临时钢横撑、缩短仰拱封闭距离等是保证大断面浅埋砂层隧道安全施工的有效方法,对其他类似工程施工提供了宝贵的工程经验。
The Guanjiao Tunnel is a controlled project of the second line of the West (Ningxia) Grid. There is a sand layer about 450m long at the entrance of the tunnel, which makes it more difficult to construct. As a result of the roof collapse accident occurred in the construction of 3 steps, the idea of 4-step construction was proposed and the 4-step excavation and support process was simulated by 3-D numerical calculation to reveal the tunnel deformation, surface settlement and initial bearing force . Through the comparison with the simulation results of three steps construction, the superiority of the 4-step scheme is confirmed. The field construction and deformation measurement results show that the construction method of large arch section and ultra- Temporary steel bracing and shortening the closing distance of invert archs are effective methods to ensure the safe construction of tunnels with large burial depth in large section and provide valuable engineering experience for other similar projects.