Abstract:

According to the performance and characteristics of shotcretebolt support and the basic theory of modern tunnel mechanics, the loadstructure model of primary support and the corresponding safety factor calculation methods are established. Firstly, the construction feasibility of three different primary support schemes including no systematic bolt support, shotcretebolt support and boltbased support is studied by taking highspeed doubletrack railway tunnel with speed of 350 km/h for example. And then, the optimized primary support parameters and the bearing capacity of the optimized secondary lining under different burial depths (i.e., 400 m and 800 m) are discussed; and based on which, the recommended values of the highspeed railway tunnel support parameters are proposed and comparison is made on calculation results before and after optimization in terms of safety factor. Some main conclusions are drawn as follows: 1) The method of using representative surrounding rock pressure in the loadstructure model is put forward, which could provide ideas for solving the surrounding rock pressure problems in design phase; and the representative values of surrounding rock pressure are with safety and economy. 2) Three calculation models are put forward, which could provide rational and effective methods for selecting and quantifying the primary support components. 3) The primary support schemes and optimized composite lining design parameters of the highspeed doubletrack railway tunnel with speed of 350 km/h are put forward; and the main bearing structures of different grades of surrounding rock and burial depths are also defined. 4) Suggestions are proposed for the burialdepthbased design of support structure parameters.

Key words: highspeed railway tunnel, support parameters, loadstructure model, safety factor method, design method