Laboratory Experiment of Upper Excavation Influence on the Existing Tunnel

Abstract

When initial depth is small and the class of surrounding rock is poor, excavation construction will strongly influence the existing tunnel. This paper uses a model test and numerical simulation methods to study the influence of excavation construction on the top of the existing tunnel. The study shows that the arch crown occurs at the largest displacement (0.33 mm) and negative moment (-1.2 kN≤m). The arch springing occurs at the largest axial force (320kN) and positive moment (0.69kN≤m). As the excavation proceeds, 3 modes have obvious displacements, axial force and bending moment of changing depth: 2.0D, 1.6D and 1.2D, respectively. The displacement, axial force and bending moment were associated with structural soundness, a high degree of tunnel and the impact on the scope is small. Numerical simulation of structural displacement, axial force and bending moment values and test values have the same variation. With shallow tunnel excavation from the vault above a certain distance, the structure stress changes. Appropriate measures to reduce the impact of countermeasures shall be taken.