Characteristics and mechanism of rockburst at five deep gold mines in Jiaodong Peninsula of China

Abstract

Rockburst in deep rock engineering poses serious threat to personnel safety and engineering. In order to reveal the rockburst characteristics in deep engineering, the rockburst investigations and rockburst mechanisms based on in-situ stress were carried out at five deep gold mines in Jiaodong Peninsula, China. At the cover depth between 400 m and 600 m, the ground pressure hazards are mainly local spalling. At the cover depth between 600 m and 1000 m, the ground pressure hazards are mainly rockburst, accompanied by serious spalling. When the cover depth is more than 1000 m, in addition to rockburst, the large area collapse occurred in some tunnels. The maximum horizontal principal stress in the northwest of Jiaodong Peninsula is the largest, indicating that the regional in-situ stress field is dominated by horizontal tectonic stress. The average maximum horizontal principal stress direction is about 105°, which is approximately perpendicular to the strike of regional metallogenic fault zone. The increase of in-situ stress is the main factor leading to the serious ground pressure hazards. The tangential stress threshold for rockburst is 8 times the tensile strength of rock at the five gold mines, which is consistent with the stress threshold (8 times tensile strength) leading to brittle failure of rock in Griffith criterion. This indicates that the strain rockburst is caused by the concentration of tensile stress in the micro-cracks of surrounding rock.