高地应力软岩隧道仰拱施作方法研究

The Study of Construction Methods of Inverted Arch under the Soft Rock Tunnel of High-in-situ Stress

为研究不同的仰拱施作方法对高地应力软岩隧道稳定性的影响,根据时速为200km/h的双线铁路隧道的标准设计图建立有限元模型,基于三台阶七步开挖法研究了四种不同的仰拱施作方法.分析了不同仰拱施作方法下隧道的拱顶、边墙及仰拱的变形和应力,进一步讨论了初期支护的安全稳定性.研究结果表明:高地应力软岩隧道三台阶七步开挖法中下台阶核心土带仰拱一次开挖,仰拱先填充碎石土后换填混凝土的施作方法最优,该方法能有效控制围岩变形,建议高地应力软岩隧道施工中采用该法;传统的仰拱施作法因初期支护封闭滞后等问题,围岩变形较大;下台阶核心土带仰拱一次开挖,仰拱中部填充碎石土的施作方法不可行,左、右边墙安全系数小于2,不满足规范要求.

In order to study the influence of different inverted arch construction methods on the safety and stability of soft rock tunnel in high in situ stress,a model is established according to the standard design drawing of the double line railway tunnel with the speed of 200 km/h,and four construction methods of inverted arch are studied based on the three bench and seven step excavation method of tunnel.The displacement and stress under different construction methods of inverted arch are analyzed.The safety and stability of the initial support are also discussed.The results show that:the optimum construction method for the inverted arch excavation is to fill the gravel soil in the inverted arch first and then replace the gravel soil by concrete in the method of one time inverted arch excavation of step down core soil belt.This method can effectively control the deformation of surrounding rock.It is suggested that this method should be applied in the construction of soften rock tunnel with high in situ stress.Because of the lag of primary support closing,the deformation of surrounding rock is larger in the traditional inverted arch construction method.The method of filling gravel soil in the middle of inverted arch in the method of one time inverted arch excavation of step down core soil belt is not feasible,because the safety coefficient of the left and right side wall is less than 2,and it fails to meet the standard requirements.