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. 