Microseismic response characteristics of overlying strata failure and unusual gas emissions in deep mining

Abstract

Unusual gas emissions constitute a critical dynamic hazard threatening mining safety. Severe fracturing within the overlying strata during deep mining substantially increases the likelihood of such incidents. A high-precision microseismic monitoring system was employed to investigate the spatiotemporal distribution and evolution patterns of microseismic events during mining operations at the 1200 mining face in Shanxi, China. This approach enabled analysis of the dynamic microseismic response characteristics linked to overlying strata fracturing and unusual gas emissions during deep mining. Microseismic events exhibited high-density distribution within 0–20 m above the coal seam, low-density distribution between 20–80 m above the seam, and within 0–10 m below the floor. Thirty-six percent of microseismic events had counts between 10 and 30, whereas 24 % ranged from 30 to 60 events. Additionally, 72.3 % of microseismic events had energies concentrated within 10³ to 10⁴ J. The caving zone (0–16 m above the coal seam) displayed microseismic events distributed laterally across its extent; this zone exhibited an intense microseismic response and high event concentration. The fracture zone (16–39 m above the seam) contained fewer microseismic events, though distribution was relatively concentrated. Within the bending subsidence zone, the microseismic response was weak, with events being scattered and infrequent. Utilizing the minimum cumulative energy threshold (9.8 × 10⁵ J) of microseismic events intercepted by the roof, we determined the advance influence distance of overlying strata fractures to be 5–20 m. Patterns of unusual gas emissions showed correlation with microseismic event magnitude, location, and distribution density across the area. This study was designed to reveal the intrinsic relationship between overlying strata fracturing and unusual gas emissions. The findings are expected to provide effective early warning systems and control strategies, facilitate real-time monitoring of mine safety, mitigate catastrophic accidents, and safeguard miners’ lives. These results offer a novel perspective on coal-rock failure–gas emission relationships at high-gas mining faces, enhancing gas prevention measures and overall mine safety.