Rockburst Characteristics and Mechanisms during Steeply Inclined Thin Veins Mining: A Case Study in Zhazixi Antimony Mine, China

Abstract

With the increase of mining depth, rockbursts have become important safety problems in Zhazixi Antimony Mine, where overlying strata exceed 560 m. Due to the small spacing between the steeply inclined veins, mining activities have great influences on rockbursts of adjacent veins. In order to study rockburst characteristics and mechanisms in Zhazixi Antimony Mine, in situ measurement, field geological survey, uniaxial compression tests, and numerical simulation are conducted to analyze rockburst proneness and simulate the elastic strain energy accumulation characteristics. Consequently, rockburst proneness criteria are established on the basis of experimental results to propose the necessary lithologic conditions for rockburst aiming to Zhazixi Antimony Mine. Rockburst dangerous districts are defined based on high stress concentration and elastic strain energy distribution characteristics in mining process obtained by theory analysis and numerical simulation. Accordingly, it is suggested that thrown-type rockbursts mainly occur in massive stibnite of ventilation shafts and stopes where the elastic strain energy exceeds 300 kJ·m−3, spalling-type rockbursts generally appear in slate of roadways where the elastic strain energy exceeds 100 kJ·m−3, and ejection-type rockbursts arise in different rock masses under a certain condition. Last but not the least, prediction results are basically consistent with statistics data of rockburst events after comparative analysis.

Characteristic Impedance and Its Applications to Rock and Mining Engineering

“…In Zhazixi antimony mine, rock burst first appeared when mining depth reached 560 m below the ground surface. When mining to 605 m depth, more and stronger rock bursts occurred (Ma et al 2018). These examples indicate that when the mining activity reached a certain depth, rock bursts may happen.…”

“…As mentioned in Sect. 7.2, strong rockbursts happened often in massive stibnite but not in other rock masses in Zhazixi antimony mine (Ma et al 2018). As shown in Table 4, the characteristic impedance Z P of the massive stibnite is 15.9 (10 6 kg/m 2 s), while the characteristic impedances of the other rock masses in the mine are smaller than 15.9 (10 6 kg/ m 2 s).…”

“…Even in a long and narrow ore body named Parta, one part was burst-prone but the other not. In Zhazixi antimony mine, strong rock bursts occurred often in massive stibnite but not in other rock masses (Ma et al 2018). These three examples indicate that rock bursts are dependent on the rock mass and mining location.…”

“…It has been reported that with increasing mining depth, both number and magnitude of rock bursts increase in many mines (e.g., Brauner 1994;He and Qian 2010;Nordström et al 2017;Ma et al 2018;Cai et al 2020;Jiang et al 2020). In general, as mining operations reach a certain depth such as several hundred meters, seismic events and rock bursts start to occur.…”

“…(1) Zhazixi Antimony Mine As mentioned earlier, strong rock bursts occurred often in massive stibnite but not in other rock masses in Zhazixi antimony mine. Based on the measured Young's modulus, density and Poisson ratio of each rock/ore from the mine (Ma et al 2018), the P-wave velocity, and characteristic impedance of each rock/ore mass can be calculated and the results are shown in Table 4. Obviously, the massive stibnite has the largest characteristic impedance up to 15.9 (10 6 kg/m 2 s), compared with other rock masses in the mine (Ma et al 2018).…”