Monitoring Analysis and Application of Large Section Soft Rock Tunnel Construction

In order to ensure the stability of surrounding rock and the safety of supporting structure system and during tunnel construction, this paper combined with the advanced geological prediction and the hole inside and outside geological observation, By monitoring and measuring the construction of a large-section soft surrounding rock highway tunnel, the data of surface subsidence, vault subsidence and convergence around the tunnel were analyzed and processed, and its distribution characteristics and variation rules were studied. The research results show that the construction method and the supporting parameter design of this tunnel are reasonable and the deformation of surrounding rock has the trend of "increase sharply→slowly→steadily" in most cases. In addition, the surface subsidence eventually approaches the steady-state value. When the tunnel face passes through the surface subsidence monitoring section 10 times B(B for the tunnel excavation width). When the tunnel face passes through the inner monitoring section 3 times B, the vault settlement and the peripheral convergence can reach about 80% of the stable value; when 6 times B, the change tends to be stable. And the peripheral convergence variation of the upper step is obviously greater than the lower step. When the distance between the first hole right and the following hole left of tunnel face is more than 5 times B, their influence can be effectively reduced. This study can provide some useful reference for the design, construction and monitoring of tunnel engineering under similar conditions.