1、Prevention and forecasting of rock burst hazards in coal mines DOU Lin-ming, LU Cai-ping, MU Zong-long, GAO Ming-shiState Key Laboratory for Coal Resource and Mine Safety, China University of Mining & Technology,Xuzhou, Jiangsu 221008, China Abstract: Rock bursts signify extreme behavior in coal min
2、e strata and severely threaten the safety of the lives of miners, as well asthe effectiveness and productivity of miners. In our study, an elastic-plastic-brittle model for the deformation and failure ofcoal/rock was established through theoretical analyses, laboratory experiments and field testing,
3、 simulation and other means, whichperfectly predict sudden and delayed rock bursts. Based on electromagnetic emission (EME), acoustic emission (AE) and microseism(MS) effects in the process from deformation until impact rupture of coal-rock combination samples, a multi-parameter identificationof pre
4、monitory technology was formed, largely depending on these three forms of emission. Thus a system of classificationfor forecasting rock bursts in space and time was established. We have presented the intensity weakening theory for rock bursts and a strong-soft-strong (3S) structural model for contro
5、lling the impact on rock surrounding roadways, with the objective of layinga theoretical foundation and establishing references for parameters for the weakening control of rock bursts. For the purpose of prevention, key technical parameters of directional hydraulic fracturing are revealed. Based on
6、these results, as well as those from deep-hole controlled blasting in coal seams and rock, integrated control techniques were established and anti-impact hydraulic props, suitable for roadways subject to hazards from rockbursts have also been developed. These technologies have been widely used in mo
7、st coal mines in China, subject to these hazards and have achieved remarkable economic and social benefits.Keywords: rock bursts; elastic-plastic-brittle model; multi-parameter premonitory; intensity weakening; strong-soft-strong (3S) structure; directional hydraulic fracturing; anti-impact hydrauli
8、c prop.1 IntroductionCoal resources are the main source of energy in China and 95% of the coal produced comes from underground mines. As the mining depth increases (about 20 m per year) and geological conditions deteriorate,the mechanical environment and basic behaviorin deep-level mining is signifi
9、cantly different from that in shallow mining and shows obvious characteristics of nonlinear dynamic instability13,which may easily lead to an increase in dynamic disa sters,such as rock burst, roofs collapsing over large areas and other problems which pose serious threats to the safety of coal produ
10、ction in mines. The rock burst is one of the typical dynamic hazards in coal mining, which is caused by elastic energy emitted in a sudden, rapid and violent way in a coal-rock mass and even can increase the possibility of other dynamic accidents such as coal and gas outburst, explosions,etc4. Rock
11、burst hazards exist in over 100 coal mines in China, especially in Fushun, Fuxin, Xinwen,Yanzhou, Kairuan, Datong, Xuzhou and Huating. For example, a serious rock burst and gas explosion accident occurred in the Sunjiawan coal mine in Fuxin, Liaoning province on Feb, 14, 2005. After the ML=2.5 rock
12、burst had occurred, a large amount of gas was emitted, which then induced a serious gas explosion and resulted in many injuries and loss of life. Thus, the safety and highly efficient production of the underground mine had been severely impactedby the rock burst.The rock burst mechanism is a quite c
13、omplicated problem. Although much significant research has been carried out around the world, from rock burst mechanism studies to rock burst forecasting and hazard control, there are still many key issues requiring further research524. Our study mainly presents recent progress in research on the pr
14、evention and control of rock bursts conducted at the China University of Mining & Technology.2 Tendencies in rock burst of compound coal-rock samplesFrom the analysis of roof and floor structures in previous rock bursts, it appears that a considerable number of rock bursts occur under conditions of
15、hard roof and floor structures. Especially hard thick sand-stone roofs overlying coal seams is the one of major factors affecting rock bursts. Under conditions of“two-hard” (hard roof and floor), the strength and thickness of the coal seam also has certain effect on the distribution of secondary str
16、ess after the excavation of a coal-rock mass. Therefore, the research on the tendency of rock bursts in compound coal-rock samples in the system of “roof- coal seam-floor”, as well as the effects of the strength and thickness of coal seams on rock burst occurrences, will greatly benefit the prevention and control of rock burst hazards. From the laboratory research on compound coal rocksamples, our results indicate that the higher the proportion of the roof c
