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.

The existence of excavation damaged zone (EDZ) generally influences the stability and safety of the underground openings. To investigate the influence of EDZ on the stability of underground excavation under dynamic stress disturbances, underground excavations with EDZs are represented by holed rock specimens with damage zones. The fracture evolution and dynamic mechanical properties of damaged holed rock specimens under dynamic loads are investigated by using the improved Split Hopkinson Pressure Bar (SHPB). The results have shown that the stress-strain curve of the rock specimens with damage zones is divided into pre-peak and post-peak stages, without compaction and elastic deformation stages. The dynamic strength, peak deformation moduli, and crack initiation stress decrease while the strain rate, absorbed energy, and failure time of holed specimens increase with increasing damage around circular holes. The failure of the holed rock specimens always start from circular holes, and specimens without or with minor damage exhibit overall tensile-shear failure. However, the failure of rock specimens with a greater damage condition mainly appears within damage zones around circular holes in the form of spalling or compression-shear failure, and the failure zone increases with increasing damage of surrounding rocks. The failure around and away from circular holes of specimens without or with minor damage is respectively characterized by intergranular and transgranular cracks. The results of the present study provide implications to the disaster prevention and support design of underground openings with EDZ.

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