Numerical Study on Rock Stability and Mechanical Characteristics of Supporting Structure of Water Tunnel with Different Buried Depths

Abstract

To explore the suitability of the supporting scheme of horseshoe tunnel affected by different buried depths in phyllite rock, the 3D numerical tunnelling simulations were conducted. The plastic zone distribution, deformation characteristics and stress field of surrounding rock and mechanical characteristics of supporting structures during the excavation process were analyzed. It was shown that the plastic zone depth, volume and deformation development of the surrounding rock are greatly limited by the shotcrete-bolt support under different buried depths. Meanwhile, the restriction proportion to the development of the plastic zone and rock deformation is slightly affected by the buried depth of the tunnel. With the increase of the buried depth of the tunnel, the reasonable shortest distance that should be reserved between the constructed lining and tunnel face also gradually increases. Combined with the calculated tunnel deformation and the classification standard proposed by Hoek, it is recommended to adopt full-section shotcrete-bolt support, and add steel arch support as the necessary supplement for the existing tunnel supporting scheme. The research results contribute to design and construction guidance for tunnels under similar geological environments.