京张高铁八达岭长城站超大跨隧道变形控制标准研究

为了确保超大跨隧道开挖过程围岩稳定和施工安全,合理确定各开挖步序的变形控制标准,采用理论分析、数值模拟实验和现场监测等方法,建立隧道变形与围岩应变相互关系的计算模型,提出基于围岩极限应变的隧道总变形控制标准,制定超大跨隧道分步变形控制标准和分级管理方法。研究结果表明:隧道围岩总变形控制标准取决于隧道围岩的极限应变;Ⅲ、Ⅳ和Ⅴ级围岩32.7 m跨度的隧道,其拱顶总沉降控制标准分别为40,90 mm和180 mm;超大跨隧道施工过程中成跨阶段的变形约占总变形的95%,成墙阶段的变形约占总变形的5%。

Study on Large Span Tunnel Deformation Control Standard for Badaling Station of Beijing-Zhangjiakou High-speed Railway

In order to ensure the stability of the surrounding rock and construction safety during the excavation of the super-large span tunnel, and to reasonably determine the deformation control standard of each excavation step, this paper uses the methods of theoretical analysis, numerical simulation experiment and field monitoring to establish the calculation model of the relationship between the tunnel deformation and the surrounding rock strain, proposes the total deformation control standard of the tunnel based on the limit strain of the surrounding rock, and formulates step-by-step deformation control standard and management method for the super-large span tunnel. The results show that the total deformation control standard of the surrounding rock of the tunnel depends on the ultimate strain of the surrounding rock of the tunnel; the total settlement control standards of the arch crown of the 32.7 m-span tunnel with class Ⅲ, Ⅳ and Ⅴ surrounding rock are 40 mm, 90 mm and 180 mm respectively; the deformation in the span-forming stage accounts for about 95% of the total deformation and the deformation of the wall-forming stage accounts for about 5% of the total deformation during the construction of the large span tunnel.