The Supportting Technology For Shallow Large Profile Neighborhood Loess Tunnels

With the large number of domestic construction of Loess Tunnel, Loess tunnel construction design has been largely improved in recent years. But researches for shallow large span small spaced highway tunnel in Loess are rare. Our study focused on the method of loess tunnel construction and the effect and selection of frame based on the Wu Xi highway peach blossom Valley tunnel,, the following work had been done:(1)The indoor experiment was carried out to study the physical mechanics properties of Loess in Peach Blossom Valley tunnel surrounding rock, thus the test section of tunnel surrounding rock was consistent in properties.(2)According to the concrete hardening experiment, the early strength of shotcrete growth law and related formula were figured out in the condition of quick hardening. Through three-dimensional numerical simulation, we could draw a conclusion that sprayed concrete rapid hardening and slow hardening conditions of the supporting ability were basically the same.(3) The30m grid experimental section was setted, including15m the Stage construction,15m the Bilateral wall method.we came to the conclusion that the grid support under the bilateral wall method had more advantages than the bench method in controlling settlement and initial supporting force through the comparison of two kinds of construction method of arch foot, vault subsidence, subsidence, horizontal convergence of surrounding rock pressure, initial supporting steel stress.(4)In the condition of bilateral wall construction, through setting the10m type steel test section,we found out that the grid supporting and steel bracing were basically at the same level with the grill supporting with steel support in the control of settlement and stress of considerable.(5) Though digital simulation of the settlement control effect of grid supporting and steel bracing in strict accordance with the construction steps and consider the shotcrete strength growth factor, we got a conclusion that there are not significant different in the vault settlement control, and steel bracing was more favorable in the control of horizontal displacement.