京张高铁八达岭长城站大跨深埋三连拱围岩压力计算方法研究

大跨度深埋三连拱隧道具有开挖跨度大、施工工序复杂、各洞室协同受力等特点,支护结构设计需要进行荷载-结构模型验算,而荷载如何确定尚无成熟的计算方法。依托京张高铁八达岭长城站三连拱隧道工程,基于普氏平衡拱基本假定并借鉴深埋双连拱隧道荷载计算方法,推导出深埋三连拱情况下围岩压力计算解析解。研究表明:三连拱隧道围岩压力由拱部松散土压力和中隔墙共同承担;中隔墙的主动支撑作用非常重要,这与双连拱隧道的受力变化规律吻合;该计算方法适用于具备一定强度的接近松散体围岩;通过解析法计算结果与现场监测数据对比分析,水平与竖向围岩压力最大相对误差分别为9.75%和10%,验证解析法计算结果的合理性。

Study on Calculation Method for Surrounding Rock Pressure of Large-span Deep Buried Three-arch Based on the Badaling Great Wall Station on Beijing-Zhangjiakou High-speed Railway

Long-span deep-buried three-arch tunnels have the characteristics of large excavation span, complex construction process and each cavern bears forces cooperatively. Usually the support structure design needs load-structure model checking calculation, but there has been no mature calculation method to determine the load. Under this background and with reference to the three-arch arch project of Badaling Great Wall Station on the Beijing-Zhangjiakou High-speed Railway, the analytical solution of surrounding rock pressure calculation under the condition of deep-buried three-arch tunnel is derived based on the basic assumption of Pu's equilibrium arch and the load calculation method of deep-buried double-arch tunnel. Research results show that the surrounding rock pressure of the three-arch tunnel is determined jointly by the loose earth pressure at the arch and the middle partition wall; the active support function of the middle partition wall is very important, which is identical to the law of stress variation of double-arch tunnel; the calculation method is applicable to surrounding rock with certain strength near the loose surrounding rock; the comparison and analysis of the analytical calculation results and field monitoring data indicate that the maximum relative errors of the horizontal and vertical surrounding rock pressure are 9.75% and 10% respectively, and verify the rationality of the analytical method.