为探讨山城轨道交通隧道下穿铁路施工措施，依托重庆市轨道交通1号线中梁山隧道进口下穿襄渝铁路2号线段，通过理论分析和数值模拟等手段，对下穿段施工方法、施工地表变形、火车荷载对初期支护安全性影响进行研究。主要研究结论如下： 1）富水强风化泥岩段隧道施工应做好防水排水系统的设置，适时施作超前支护并尽快封闭断面； 2）在下穿段选用三台阶七步法，既可满足沉降限值的要求，又可提高效率、节省成本； 3）火车荷载会影响隧道结构的承载能力，在埋深19 m的富水强风化泥岩中施工地铁隧道，初期支护结构安全性仍能满足要求； 4）通过现场实测，证明施工沉降控制效果明显，保障了襄渝铁路2号线的运营安全；5）为类似施工采取相应措施控制地表沉降，保护周边铁路及隧道结构的安全提供了一定的理论依据。

The construction technologies, ground surface deformation and the influence of the train load on the safety of the tunnel primary support are analyzed by means of theoretical analysis and numerical simulation, with the construction of the entrance section of Zhongliangshan tunnel on No. 1 line of Chongqing MRT crossing underneath No. 2 line of XiangyangChongqing railway as an example. Conclusions drawn are as follows: 1) The waterproofing and drainage system is very important for the tunnel section in highlyweathered waterrich mudstone ground. Advance support has to be made in time and the reinforcement structure should be closed as soon as possible. 2) The settlement requirement can be met, the construction efficiency can be improved and the cost can be reduced by using sevenstep threebench excavation method. 3) The train load has some influence on the bearing capacity of the tunnel structure. However, the primary support of the tunnel under 19 mdeep highlyweathered waterrich mudstone cover is safe. 4) The site monitoring results show that the settlement control is effective. 5) The paper can provide theoretical reference for the control of the ground surface settlement and the protection of nearby railways and tunnels in similar future works. 