Study of Bench Method's Geometric Parameters Optimization in Weak Broken Wall Rock and Large Cross-section Tunnel

In the soft rock tunnel excavation broken.Bench method is more dangerous than CD and CRD method,easy to produce the large deformation,landslides accident.But because it can shorten the construction period,so often be used by construction units.As all we know,the bench height plays an important role in the bench method optimization.This paper based on the railway tunnel,by means of the numerical simulation method to optimize the heights of up step in the bench method.By comparing the 0.55H,0.60H,0.65H,0.70H,0.75H five different height in the tunnel excavation of the influence of lining and rock,it is concluded that the 0.65H is the appropriate bench heights in the construction which is good for the engineering construction to provide the reference.