Abstract:

In order to understand the stressstrain behavior of tunnel surrounding rock and supporting structure of in sandy cobble ground and based on the Qinghai Xunlong Expressway Gongboxia tunnel, the 3D simulation of the tunnel construction in sandy cobble stratum is performed by PFC3D. The stressstrain behavior of surrounding rock and supporting structure in sandy cobble Stratum is mainly studied with the premise of densely packed short pipe shed presupport and threebench reserved core soil method, and which is compared to the field measurement. The results show that: (1) when tunnel is excavated, the range of rock stress concentration gradually changes from the vault to the hance, until the skewback, and the corresponding plastic zone range is continuously expanded. Besides, the densely packed short pipe roof has a certain "obscuring effect" on the development of the plastic zone. (2) the deformation laws of the surrounding rock for transverse and longitudinal are consistent, which mainly converge to the tunnel free face. And the beam arching effect formed by the densely packed short pipe roof restricts the development of the displacement in front of the tunnel face; (3) the initial support deformation laws obtained by the two methods are consistent, both showing staged changes. The cumulative value of the vault settlement is greater than that of the surrounding convergence, and the final deformation of which can both meet the specification limit.

Key words: tunneling engineering, sandy cobble stratum, threebenchreserved core soil method, PFC3D DEM, stressstrain behavior, field measurement