Analysis of microseismic activity rules of underground mining in Zijinshan Gold and Copper Mine

Frequent underground mining activities have caused repeated disturbances to the stability of roadway surrounding rocks, exacerbating the risk of roadway surrounding rock damage. The Zijinshan Gold and Copper Mine employs large-diameter deep-hole filling mining for underground mining, resulting in lateral ore body collapses. With a maximum single blasting charge of 4 tons, these blasting activities create significant disruptions, leading to varying degrees of damage in localized roadway surrounding rock areas. To address this issue, a 32-channel microseismic monitoring system is established, taking into account the layout of the Zijinshan Gold and Copper Mine. This system is used to study the spatio-temporal evolution of microseismic events in the roadway surrounding rocks during the mining process and to assess the risk of roadway surrounding rocks damage. The results indicate that the positioning error for microseismic events in the prominent ground pressure area of the eastern wing of the ore body is less than 8 meters. The alteration of rock bodies in the eastern wing of the ore body, along with mining activities, plays a crucial role in shaping the characteristics such as size and morphology of microseismic event clusters in the −100 m to +100 m range of the Zijinshan Gold and Copper Mine. Microseismic events predominantly concentrate in the −50 m to +100 m range of the ore body’s eastern wing, with active mining areas distributed near the microseismic event clusters. Notably, microseismic lgEI, displacement, and density nephograms of microseismic event exhibit distinct distribution patterns. In the middle section of the −50 m section, the 7# mining area experiences higher stress levels, relatively larger displacements, and a concentration of microseismic events. Consequently, this area presents a relatively higher risk of mining-related disasters. Field investigations into roadway surrounding rock damage have revealed instances of rib spalling, cracks, and other damage in roadway sections along the vein roadway with the 9# vein and E3# vein intersections at the 50 m section and at the intersection of the −50 m section along the vein roadway with the 7# vein and E3# vein intersections. These occurrences of roadway surrounding rocks damage closely align with the distribution of microseismic lgEI and displacement concentration zones. The research findings are instrumental in guiding the optimization of support parameters at the Zijinshan Gold and Copper Mine, ultimately holding significant importance for ensuring safe mining operations.