Delineation of large localized damage structures forming ahead of an active mining front by using advanced acoustic emission mapping techniques

Abstract

a b s t r a c tWe applied advanced mapping techniques to 291 230 acoustic emission (AE) events as small as around M À 4 that were recorded over 50 days by an ultra-high resolution network close to the active front of a tabular mining stope being advanced northward at 1 km depth in the Cooke 4 Gold Mine in South Africa. We first applied joint hypocenter determination (JHD) to improve absolute locations, and then applied the double-difference relative location algorithm to the JHD output. These steps resolved the seemingly continuous, dense cloud of AEs that extend about 20 m ahead of the stope front into several discrete, steeply dipping tabular clusters a few meters thick and 10-30 m in dip extent, separated by quiet intervals a few meters thick. The clusters have a strike parallel to the stope face and a dip of about 65°, resembling commonly observed large shear fractures along the plane of maximum shear (Ortlepp shears). In general, the activity of the clusters changed in similar ways as the stope face advanced, but each cluster remained stationary and the gaps between clusters were impressively quiet. This study demonstrates that high-resolution AE mapping can delineate the formation of large structures of localized damage in the highly stressed intact rock mass ahead of the stope face, a process that may culminate in hazardous seismic events.

Analysis of the Gutenberg-Richter b-values of overlapping seismic clusters with application to Cooke 4 gold mine

“…Many events with a useable signal-to-noise ratio up to 50 kHz were recorded and AEs with magnitudes as small as MW-5.3 were detected. A catalogue of ~1.02 million seismic events collected from 10 July 2011 to 25 March 2012 was used to study the frequency-magnitude distribution of acoustic emissions, , the formation of damage structures ahead of the mining front, Moriya et al (2015), the unexpectedly frequent occurrence of very small repeating earthquakes, Naoi et al (2016), quasi-static growth of a slip-patch on a pre-existing fault and the properties of the rupture zone revealed by repeating events, Yamaguchi et al (2018). found that a Gutenberg-Richter law with b  1.2 was valid between MW -3.7 and 0 for acoustic emissions around the mining front, where MW is the moment magnitude.…”

Acoustic Emission/Seismicity at Depth Beneath an Artificial Lake after the 2011 Tohoku Earthquake

“…Acoustic emission (AE)/seismicity is important for evaluating the stability of geological structures; for instance, the delineation of fracture systems from AE activity in geothermal reservoirs is indispensable for thermal energy extraction [1]. The stability evaluation of fractures during hydraulic stimulation in geothermal reservoirs is necessary to avoid inducing large AE events, where the relationship between large AE events and the pore-pressure distribution in reservoirs is studied [2]. The stability of geological structures is also important from the viewpoint of disaster prevention.…”

Spatial Modeling of the Influence of Mining-Geometric Indices on the Efficiency of Mining

“…The studies assess (Korobiichuk, 2013;Korobiichuk & Iskov, 2013;Pershin & Ulyakov, 2015;Moriya et al, 2015;Bakka & Ilchenko, 1992;Karasev & Bakka, 1997;Korobiichuk et al, 2016a, b;Sobolevskyi et al, 2016;Kosolapov, 1990) that drilling takes 50-80% of the total time of block stone mining. Thus, the increase of the time spent on drilling can considerably reduce the mining works efficiency and, as a result, it can reduce the overall profitability.…”

“…Thus, the increase of the time spent on drilling can considerably reduce the mining works efficiency and, as a result, it can reduce the overall profitability. The main criteria to evaluate the efficiency of mining are the cracks of a massif (Moriya et al, 2015;Bakka & Ilchenko, 1992;Karasev & Bakka, 1997;Korobiichuk et al, 2016a, b;Sobolevskyi et al, 2016;Kosolapov, 1990;Mosch et al, 2011;Caranassios et al, 2000;Rahimi & Nygaard, 2015;Luodes & Sutinen, 2011) which are estimated by means of different factors. Specific fracturing is one of the main factors which, along with a blocks output, is used to evaluate the deposit.…”

“…It also helps to plan the volumes of efficiently extracted product. A small error can occur but it depends on the method of block output forecasting; the known forecasting methods are numerous (Pershin & Ulyakov, 2015;Moriya et al, 2015;Bakka & Ilchenko, 1992;Karasev & Bakka, 1997;Korobiichuk et al, 2016a, b;Sobolevskyi et al, 2016;Kosolapov, 1990;Mosch et al, 2011;Caranassios et al, 2000;Rahimi & Nygaard, 2015). At the same time, considering the efficiency of mining complexes, the actual productivity is used as the main index, and it is the function of working cycle duration.…”