Study On Supporting Structure In Cohesive Soil Tunnel Of High Water Content

Due to the effect of construction method, supporting opportunity and construction technology of soil tunnel on supporting effect of systematic bolts, as well as the disadvantages of high water content cohesive soil layer bolts such as the difficulty of blasthole completion, bad grouting effect and low anti-drawing strength, based on project of the Tianhengshan highway tunnel, the paper is giving a viewpoint that it is not setting systematic bolts of clay tunnel, the primary support is a new supporting structure that consist of steel arch(steel grid), shotcrete, reinforcing mesh, locking sanchor pipe and vertial connecting steel bar.To study the deformation and stress of the new supporting structure and the feasibility of the whole lining structure, taking two methods, which were field test and finite-element simulation, to make comprehensive evaluation of tunnel structure on its safety, stability and economy.The field test was based on V and VI class surrounding rock, and the content of monitoring measurement included clearance convergence, vault crown settlement, surrounding rock pressure, shotcrete stress, steel arch stress, vertial connecting steel bar stress, pressure between primary lining and secondary lining, concrete and steel stress of secondary lining and convergence measurement of secondary lining. The result showed that the deformation and stress of supporting construction was in the allowable range, the tunnel lining was safe and had enough safety margins when it was not setting systematic bolts.The deformation and stress of tunnel supporting construction were analyzed by finite elements analysis soft (MIDAS/GTS) in the case of setting no systematic bolts. The result showed that the shotcret and secondary lining had enough safety margins, the stress of steel arch and locking stringer tube were significant, the deformation of surrounding rock was stabal.According to the analysis on monitoring measurement and finite elements analysis result, all result showed that the new supporting structurewere in the allowable range, the secondary lining was safe and had enough safety margins when it was not setting systematic bolts. If the systematic bolts are abandoned in VI class surrounding rock, the construction expenditure can be reduced at 8.9%, and the construction period can be reduced about at 10%.