Study Of Construction Technology Of The Portal Of New Maomaoying Tunnel On The Second Zhuzhou-Liupanshui Railway Line

On the element of the railway tunnel portals, the paper primarily studies the basic and the auxiliary construction methods about it, and makes a series of mechanical analyses on these methods, then the factors to choose construction methods and the support parameters are summarized in this paper. An example comes from engineering facts is put forward to discuss tunnel portal construction methods.The paper introduces the progress and the statue quo of tunnel portal construction, discusses the condition to employ full face method, bench cut method, single side heading method and double sides heading method of portal construction, points out advantages and disadvantages of these methods. The order to adopt these methods of single track, double track and tri-track tunnel in shallow-depth, uneven pressure and incompact ground is also advised after compare.Tunnel portals are always locate at the complex geography condition ground, so auxiliary construction methods are needed to reinforce it. The paper discusses the employing condition, mechanical principle, reinforce effect, economic guideline and construction requirements of various auxiliary construction methods in surface ground and inside tunnel, then summarizes the design parameters of these methods and illuminates how to choose them.Using FEM(Finite Element Method), the paper makes mechanical analyses on bench cut method and side heading method, it also makes mechanical analyses on some auxiliary construction methods, such as big pipe-roof protection, horizontal roll-spraying, big and small angle pipe-roof protection and surface grouting.The paper describes the application of various construction methods in new Maomaoying tunnel in the end.