Effect of the Location of Fault Fracture Zones on the Stability of Symmetrical Submarine Tunnels

Wei Fang,Chang Wang,Gang Wang

doi:10.3390/sym13071111

Abstract

In this paper, we aim to reveal the influence of fault fracture zones on the stability of submarine tunnels and the surrounding rock under different water and drainage measures. Firstly, four typical working conditions of submarine tunnels intersecting with fault fracture zones were selected. On the basis of the typical cross section of the intersections of submarine tunnels and faults, they were divided into four working conditions. Then, the displacement and plastic zones of the surrounding rock of the tunnel were studied, and the stability of the rock surrounding the submarine tunnel was discussed. This research structure indicates that the bending moment and axial force of the lining structure of the submarine tunnel increase with increasing sealing degree, but the safety factor exhibits a downward trend. When the fault fracture zone goes through the section above the tunnel axis, the bending moment and axial force at the lining vault are greater than the other working conditions, and the displacement of the surrounding rock at the vault and spandrel is prominent. When the fault fracture zone completely passes through the tunnel, the safety factor of the lining structure is at its lowest, and the displacement of the surrounding rock at the arch waist develops laterally. When the fault fracture zone passes through the part below the tunnel axis, the arch foot displacement converges significantly, and the surrounding rock displacement exhibits a downward inclination. In addition, the plastic zone is mainly developed in the arch and the shoulder. These research results provide a reliable reference for tunnel design and excavation support.

Highlights

As an important transportation method, submarine tunnels are a major development trend in future transportation
When the upper half of the submarine tunnel is located in the fault fracture zone, that is, Working condition 1, the tensile damage area of the vault increases significantly, and the plastic zone of the arch shoulder is more prominent
When the lower half of the submarine tunnel is located in the fault fracture zone, that is, Condition 3, the plastic zone at the arch foot and the inverted arch have a wide distribution range

Summary

Introduction

As an important transportation method, submarine tunnels are a major development trend in future transportation. Wang et al [10] considered the permeability of seawater using the finite element limit analysis method, and analyzed the stability of the Qinghai-Huanghai Submarine Highway Tunnel with respect to the local fractured zone before and after grouting reinforcement. Wang and Li [16] studied the influence of different grouting reinforcement materials and different thicknesses of grouting reinforcement circles on the stress and deformation of the surrounding rock and the initial support of the tunnel when the tunnel passes through fault fracture zones using the three-dimensional finite element method. When submarine tunnels cross fault fracture zones, the effects of Symmetry 2021, 13, 1111 different degrees of water and drainage measures on the stability of the submarine tunnel and the surrounding rock need further study

Engineering Geological Characteristics

Analysis of the Influence of the Fault Fracture Zone on the Plastic Zone

Conclusions