Influence of confining pressure-dependent Young’s modulus on the convergence of underground excavation

Abstract

The actual convergence of an excavation located in fractured rock mass or the soft rock is largely different with the theoretical result in many cases. Experimental results showed that the influence of confining pressure on Young's modulus is very significant. This paper attempted to illustrate the influence of the confining pressure-dependent Young's modulus in the ground reaction analyses of mountain tunnel. Firstly, the relationship between Young's modulus and confining pressure was described as a non-linear function according to the test results. Based on the plane strain axial symmetry assumption and the incremental theory of plasticity, equilibrium equations and compatibility equations of rock mass around a circular tunnel were deduced theoretically. Based on fourth Runge-Kutta method, a semi-analytical solution was achieved. Considering the effect of confining pressure on Young's modulus, the stress and deformation of rock mass around tunnel was calculated by both analytical and numerical methods. The influence of confining pressure-dependent Young's modulus in surrounding rock was estimated quantitatively. Finally, Tawara saka Tunnel in Japan was taken as an example to explain the influence of confining pressure-dependent Young's modulus. The results showed that the error with respect to the monitoring data was largely reduced with the confining pressure-dependent Young's modulus model, which indicated the necessity of considering the non-uniform distribution of Young's modulus.

Key principles of stress control method

“…In the unexcavated state, the surrounding rock remains stable under the in-situ stress. Excavation has the following two main effects: (1) stress redistribution (Figure 1b) including radial stress decrease and tangential stress concentration [7,8] ; and (2) surrounding rock degradation (Figure 1c) [9][10][11] . As the excavation removes the rock inside the tunnel, the radial stress at the tunnel wall is instantly reduced to 0 and tangential stress will concentrate [12,13] ; In deep tunnels, stress redistribution can result in the occurrence of a plastic zone in the vicinity of the tunnel (Figure 1c)under stress redistribution [14] .…”

Research and Control of Underground Pressure Law of Coal Mining Face in Soft Rock Strata Based on Neural Network under the Background of Wireless Network Communication

“…Based on the fourth Runge-Kutta method, a semianalytical solution was obtained. Considering the influence of confining pressure on Young's modulus, analytical and numerical methods are used to calculate the stress and deformation of the rock mass around the tunnel [4]. Based on field tests, case studies, and numerical modeling, Zhang et al conducted a comprehensive investigation of the ground stability of the deep gate road buried 1 km deep.…”

Asymmetrical Deformation Mechanisms in Layered Inclined Surrounding Rock of Roadways

“…Wu et al [37], Wu et al [38], and Jia et al [39] studied the non-uniform deformation with good layering through similar simulation experiments. Li et al [40] and Wu et al [41] think that the influence of confining pressure on Young's modulus is very significant. Zhang et al [42] investigated the difference between uniform radial and non-uniform convergence deformation patterns on the surface settlements and lateral deformation of soil.…”