Abstract: In the process of construction of superlarge crosssection tunnel with weak surrounding rock, bench method will probably cause serious collapse, but it can effectively shorten the construction period. For the sake of safety, the bench method, especially the determination of the height of the bench, is worth to be studied. The construction process of railway tunnel in superweak surrounding rcok excavated by bench method with different bench heights is simulated by means of 3D numerical simulation method. The crown settlement, horizontal convergence and deformation of tunnel face under different bench heights are compared. The rules of mechanical effect in the construction process of bench method. The paper can provide references for similar projects in the future.

Key words: super large section, railway tunnel, weak and broken surrounding rock, bench method, bench height optimization, numerical simulation