Evaluation of Excavation-Damaged Zone around Underground Tunnels by Theoretical Calculation and Field Test Methods

Abstract

Excavation-damaged zones (EDZs) induced in underground mining and civil engineering potentially threaten tunnel safety and stability, and increase construction and support costs. In this paper, an investigation of the excavation damaged zone (EDZ) around roadways in Fankou lead-zinc mine in Guangzhou, China is performed by applying a seismic velocity method accompanied by SET-PLT-01 nonmetallic ultrasonic detector. Meanwhile, the in situ stress in the mining area was measured based on the stress relief method with the Swedish high-precision LUT system. The results indicate that the stress field is dominated by the maximum horizontal tectonic stress, and the extents of the EDZ on the roof-floor region are greater than that on the sidewall. In addition, both of the in situ stresses and EDZs show an increasing trend with an increase of depth. Analytical solutions of EDZ around circular openings in the brittle rock mass subjected to non-hydrostatic stress fields are presented in terms of the Mohr–Coulomb and generalized Hoek–Brown criteria, and validated by several cases mentioned above. The extents of EDZ solved by closed-form solutions were found to be in a great agreement with those obtained in the field. Finally, a series of parametric studies are conducted to investigate the effects of cohesion (c), friction angle (φ), geological strength index (GSI), mi, uniaxial compressive strength (σc), and disturbance factor (D) on EDZ. It is shown that the effects of c, φ, GSI, and σc are significant; however, more attention should be paid to consider the dynamic disturbances induced by mechanical drilling, blasting, and seismic waves in tunnel excavations or operations.

Long-term degradation, damage and fracture in deep rock tunnels: A review on the effect of excavation methods

“…The extent evaluation of these zones must be taken into account since they can change with time [39,40,41,18]. In addition, they influence considerably the stress field in roof region of tunnels [42]. The view of stress-strain curve (Fig.…”

Numerical Study on Damage Zones Induced by Excavation and Ventilation in a High-Temperature Tunnel at Depth

“…During the simulation, a sim- The problem of deep rock excavation engineering, especially the EGS-E engineering, has two main characteristics simultaneously: high in-situ stress and high temperature conditions. For the former, many researchers studied the stress redistribution and damage extent of surrounding rock due to excavation by relying on empirical approach [17], numerical simulation [18,19] and theoretical calculation [20]. For the latter, relevant studies focused on the temperature evolution of surrounding rock [21], effective ventilation distance [22] and heat insulation [23] in tunnel ventilation.…”

Effect of Axial In-Situ Stress in Deep Tunnel Analysis Considering Strain Softening and Dilatancy

“…Mineral resources are an important source of energy, and their development is shifting to deeper areas [1][2][3], increasing the depths of the tunnels excavated for the exploitation of mineral resources. Statistically, deep tunnels account for approximately 30% of the tunnels constructed each year, and 70% of these tunnels will need to be repaired owing to large deformations of the surrounding rock masses under high in-situ stress conditions, which greatly increases costs [4].…”