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在既有隧道下进行浅埋隧道开挖会引起地层产生位移,继而导致既有隧道变形。由于既有隧道与地层刚度差别巨大,常规的解析法无法计算存在不同刚度的地层位移场。基于镜像法,采用当层法对既有隧道刚度进行等效,建立综合考虑新建隧道-岩土体-既有隧道三者相互作用的计算模型。以北京地铁10号线国贸站-双井站区间下穿既有1号线区间工程为例,采用该计算方法,研究新建隧道下穿施工对地层及既有隧道的影响。研究表明,计算结果与实测变形吻合较好,解析解能很好的解释既有隧道对地层变形的阻隔和扩散作用。研究成果为下穿施工引起的既有隧道及地层沉降计算提供了一种新的解析方法。
The excavation of shallow tunnel under the existing tunnel will cause the displacement of the formation, which will lead to the deformation of the existing tunnel. Due to the huge difference between the existing tunnels and formation rigidity, the conventional analytical method can not calculate the formation displacement field with different stiffness. Based on the image method, the layer method is used to calculate the stiffness of the existing tunnel, and a calculation model considering the interaction of the new tunnel, rock mass, and existing tunnel is established. Taking the section of Guomao Station and Shuangjing Station under Beijing Metro Line 10 as an example, this study uses the calculation method to study the influence of new underpass construction on the strata and existing tunnels. The results show that the calculated results are in good agreement with the measured deformations, and the analytical solution can well explain the barrier and diffusion effects of the existing tunnels on formation deformation. The research results provide a new analytical method for calculating the settlement of existing tunnels and formations caused by construction underneath.