京张高铁八达岭长城站大跨度深埋三连拱隧道设计及施工方法研究

目前三连拱隧道衬砌荷载尚无成熟的计算方法且类似工程施工经验相对较少,以京张高铁八达岭长城站为例,研究在V级围岩地质条件下,大跨度深埋三连拱隧道设计计算方法及合理的施工工序。依据普氏平衡拱理论并借鉴双连拱隧道围岩荷载计算方法,提出深埋三连拱隧道围岩荷载模型,通过建立有限元模型,分析三连拱隧道的合理施工工序。研究表明:三连拱隧道围岩压力可以看作拱部松散土压力及中隔墙所承受的压力之和;三连拱施工工序推荐采用先侧洞后中洞的工序,对于施工过程中保持围岩及支护结构体系的稳定较为有利;通过右洞围岩压力计算结果与现场检测结果对比分析,围岩压力最大相对误差在10%以内,全施工阶段监测情况一切正常,验证了解析法计算结果的合理性及施工工序的优越性。

Research on Design and Construction Method of Large Span Deep Buried Three-arch Tunnel on Beijing-Zhangjiakou High-speed Railway

At present, there is no mature calculation method for the lining load of the three-arch tunnel and less experience in similar engineering construction. With reference to Beijing-Zhangjiakou High-speed Railway Badaling Great Wall Station, design calculation methods and reasonable construction procedures for large-span deep-buried three-arch tunnel under the V-class surrounding rock geological conditions are studied. According to the Platt balance arch theory and the calculation method of surrounding rock load of double-arch tunnel, the surrounding rock load model of deep-buried three-arch tunnel is proposed. By establishing the finite element model, reasonable construction procedures of the three-arch tunnel are analyzed. The research shows that the surrounding rock pressure of the double-arch tunnel can be regarded as the sum of the loose soil pressure of the arch and the pressure of the middle partition wall; the first-hole-then-middle-hole method is recommended in the three-arch construction process to effectively maintain the surrounding rock and stabilize the retaining structure system during the construction process; the comparison between the calculation results of the surrounding rock pressure and the on-site test results indicates that the maximum relative error of the surrounding rock pressure is within 10%, and the monitoring situation is normal in the whole construction stage, which verifies the reasonable calculation result of the analytical method and the superiority of the construction process.