Numerical Study on Comparison and Selection of Water Tunnel Section Types

Abstract

In order to study the mechanical deformation response law and stability difference of surrounding rock induced by the unloading effects of tunnel excavation with different section types, the 3D numerical tunnelling simulation was conducted. The results show that the plastic zone depth and deformation value of the surrounding rock of the circular tunnel are the smallest, and its stress distribution is uniform. The plastic zone depth and volume of the surrounding rock of the horseshoe-section tunnel are slightly larger, the rock deformation is about 10% larger than that of the former, and its stress distribution is relatively uniform. However, the plastic zone depth of the surrounding rock of the gate-section tunnel is 0.7-1.2m larger than that of the circular tunnel, and plastic zone volume increases by about 28.5%. Meanwhile, the surrounding rock deformations at the sidewall and floor of the gate-section tunnel are larger, and its deformation gradient is higher. The stress concentration phenomenon at the intersection of the floor and the sidewall is also significant. Therefore, the surrounding rock stability of gate-section tunnel is considered to be most unfavourable among the three tunnel section types. In consideration of tunnel stability, construction difficulty and economy, the horseshoe section type is recommended.