| The section of single-hole three-lane highway tunnel is mostly large span flat. In adverse geological area surrounding rock stability is poor, coupled with the effects of flat section form, construction of large span tunnel become more difficult, in the construction process extremely prone to instability and failure of surrounding rock.Based on the mountain tunnel, the paper firstly research and analysis the mechanical behavior and the surrounding rock stability in the construction of slag large span tunnel through the thick layer. Then detailed analysis the level of surrounding rock and tunnel excavation methods of tunnel in the through region.Secondly, make the use of FLAC3 D combine with the characteristics of the tunnel project to establish 3D numerical model, and simulation analysis the three-bench seven-step excavation method footage of the construction cycle deformation features of step tunnel vault, horizontal displacement of arch and the first principal stress situation of lining supporting structure.Then, through the tunnel section vault and the arch of the foot of the monitoring data regression analysis, and compare the regression value and the simulation results, obtain a variation of regression curve can reflect the surrounding rock deformation regularity. The simulation results in line with the surrounding rock deformation, and the surrounding rock in the construction process is basically in steady state.Finally, the analysis results of thick slag layer is processed in accordance with paragraph surrounding rock fracture zones surrounding rock, with three-bench seven-step excavation method is a reasonable choice. Take reasonable advance support method according to the geological survey report and the results of numerical simulation to ensure stability of surrounding rock, the mechanical properties of the supporting structure changes are allowed within the safe range. The results have some reference value for similar projects. |
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