Study on the Deformation Mechanism of a Soft Rock Tunnel

The large deformation of soft rock tunnel is one of the key problems to be overcome in the tunnel construction stage.In the present study,the deformation mechanism of a representative tunnel and some related countermeasures are investigated using field tests and engineering geological analysis.Owing to the scarce performances of methods based on other criteria such as small pipe spacing,anchor bolt length and steel frame spacing,a new support scheme is implemented and optimized.Results show that shear failure and bedding sliding are produced under high horizontal stress conditions.The low strength of the surrounding rock results in the uneven convergence of both sides of the tunnel.With the aforementioned new support scheme,however,most of such problems can be mitigated leading to good stability properties and ensuing economic advantages.