Roadway Stagger Layout for Effective Control of Gob-Side Rock Bursts in the Longwall Mining of a Thick Coal Seam

Abstract

Currently, rock bursts pose a serious threat to the safety of miners and equipment in underground coal mining operations, especially in China. The number of coal mines with rock burst hazards is increasing year by year with no signs of letting up. By 31 December 2013, there were 142 coal mines in China which had experienced rock bursts. Each year, rock bursts cause considerable economic loss and enormous casualties. For instance, a rock burst induced by a large thrust fault caused 10 deaths and trapped 75 people on 3 November 2011 during the headgate excavation of LW21221 in Qianqiu coal mine, Yima City, China (Cai et al. 2014a, b; Li et al. 2014). Rock bursts are serious not only because the hazard itself can cause damage, but because it can cause a series of secondary disasters, such as coal and gas outbursts, and gas explosions. The most serious gas explosion recorded to date killed 214 people, injured 30 people, and caused a direct economic loss of U49.689 million. It happened on 14 February 2005 in Sunjiawan coal mine, Fuxin City, China. Investigation revealed that the gas explosion was induced by a rock burst (State Administration of Work Safety, State Administration of Coal Mine Safety 2005). Existing research mainly concentrates on the monitoring, prediction, and prevention of rock bursts (Adoko et al. 2013; Cai et al. 2014a, 2014b; Kornowski and Kurzeja 2012; Mu et al. 2013). Control measures against rock bursts are usually passive and include: de-stress blasting (Konicek et al. 2013), directional fracturing (He et al. 2012a), large-diameter drilling (Li et al. 2014), etc. These measures are time-consuming and only reduce rock burst potential without complete elimination of the hazard. The latest statistical data (Pan et al. 2013) show that 87 % of rock bursts occurred in roadways in China’s coal mines. Compared with the 72.6 % seen from previous statistics (Dou and He 2001), this proportion has increased. Among roadway rock bursts, gob-side rock bursts (GRBs) (i.e., rock bursts occurring in gob-side roadways) account for the majority. For example, the eight rock bursts in the No. 17 coal seam of Xing’an coal mine, Hegang City, China, caused damage to the tailgate and the longwall face eight and two times, respectively. However, the headgate was not damaged at all (see Fig. 1a). The 22 rock bursts in the No. 17 coal seam of Junde coal mine, Hegang City, caused damage to the tailgate, the longwall face, and the headgate 18 times, five times, and once, respectively (see Fig. 1b). Both tailgates in the two coal mines are gob-side roadways. It is common in other coal mines that GRBs account for the majority of rock bursts because gob-side roadways bear a higher stress. If GRBs are controlled effectively, rock burst hazards will be significantly mitigated. In this work, a case study of Yuejin coal mine (YCM) in Yima City, China, was analyzed to ascertain whether, or not, roadway staggered layouts could control GRBs. The aim of this study was to deduce whether, or not, this & Lin-ming Dou lmdou@cumt.edu.cn; kdlzl2010@163.com