Research On Deformation Of Rock And Reasonable Supporting Structure In MingYaZi Tunnel

The MingYazi tunnel is the control project on theShiYan-TianShui highway, primary support has a serious invasion deformation in construction process, the most point achieved 1200mm,which has affected the project quality, restricted the project progress, threaten the personal security, so, this paper based on theoretical analysis, combines the site monitoring with numerical simulation method, respectively studied the three structural form and construction method, and obtained the following achievement:(1) the tunnel section adopt the form of straight wall with not closed invert of primary support, by three-step construction method, the total deformation of the arch is larger, right arch foot maximum subsidence reach to 264mm.(2) the tunnel section adopt the form of straight wall with closed invert of primary support, by three-step construction method, the deformation of the arch has improved, but the effect is not very clear, maximum subsidence occurred in the left arch waist for 151mm.(3) the tunnel section adopt the form of curved wall with closed invert of primary support, by three-step construction method, the deformation of the arch has significantly improved, effectively control the deformation, maximum subsidence occurred in the right arch waist for 85mm.(4) the surrounding rock stability and support effect monitoring and measuring was carried in YK214 +011 section, the results showed that under the condition of soft rock without systematic bolts, the supporting structural style that is consist of steel arch, shotcrete, reinforcing mesh, locking anchor and vertial connecting steel bar is stable, no systematic bolts is feasible.(5) The deformation and stress of tunnel supporting construction were analyzed by finite elements analysis soft (MIDAS/GTS) in the case of the two excavation methods and support mode. The results show that the primary support invert closed and adopting entire excavation could well control deformation, the structure stress distribution is more reasonable.According to the above research results,the MingYazi tunnel uses the lining curved and the primary support invert closed, uses the supporting structural style that is consist of steel arch,shotcrete,reinforcing mesh, locking anchor and vertial connecting steel bar,uses the three steps of construction method, by the invert trestle, carries on entire excavation, which may well control deformation, and guarantee supporting structure stability.At present, the Ming Yazi tunnel excavation works well in this plan, will have the guide and the reference value to the next similar tunnel design and construction.