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Numerical analysis on rules of dynamic gas emission during boring process
Published in Heping Xie, Yuehan Wang, Yaodong Jiang, Computer Applications in the Mineral Industries, 2020
K. Wang, Q.X. Yu, C.L. Jiang, Y.Q. Wu
The present studies of outburst have shown that gas pressure is the main power for initiating outburst; coal strength is the main factor for preventing outburst from occurring; and the permeability coefficient of coal seam which has outburst risk is far smaller than that of coal seam which has no outburst risk. Consequently based on the rules of dynamic gas emission during boring process, the outburst danger of coal seam can be qualitatively determined according to the following laws: If the volume of gas emission is very large but with quite low declining rate, or if the section of hole without gas emission is relatively long (namely the phenomenon similar to “breathlessness” is relatively obvious), the possibility of outburst occurrence is low.If the volume of gas emission is relatively large, and the peak points and valley points on the curve of dynamic gas emission are not obvious and occur relatively late, or if the volume of gas emission is rather small, meanwhile there does not occur peak point but occurs clear shape similar to “grooves” on the curve corresponding to the period when the boring process is paused, the possibility of outburst occurrence is relatively high.
Monitoring, assessment and mitigation of rock burst and gas outburst induced seismicity in longwall top coal caving mining
Published in Ömer Aydan, Takashi Ito, Takafumi Seiki, Katsumi Kamemura, Naoki Iwata, 2019 Rock Dynamics Summit, 2019
S. Durucan, W. Cao, W. Cai, J-Q Shi, A. Korre, G. Si, S. Jamnikar, J. Roser
Although high gas content coal seams may not store much elastic strain energy, the presence of high-pressure gas may provide sufficient energy to break coal and eject a considerable amount of coal-gas mixture into mine openings, referred to as gas outbursts or uncontrolled gas emissions. Since the first documented coal and gas outburst occurred in the Issac Colliery in France (1843), as many as 30,000 outbursts have occurred in the world coal mining industry (Lama and Bodziony, 1998). Using in situ borehole pressure measurements, Diaz Aguado and Gonzalez Nicieza (2007) have concluded that the gas outburst occurrences in the Asturias coal basin of Spain were controlled by the mining stresses and gas pressure build up in virgin areas. As the understanding of the structural conditions and mechanisms leading to gas outbursts improve, more effective preventative measures are being developed and implemented. In recent years, researchers at CSIRO in Australia carried out a series of projects investigating coal and gas outbursts, developed a coupled geomechanical-flow model and applied to field conditions at a number of Australian coal mines (Wold and Choi, 1999; Choi and Wold, 2002; Wold et al., 2008). Although less often, the European coal industry still experiences gas outburst events, which lead to loss of production, and even loss of life.
Dynamic Phenomena
Published in William G. Pariseau, rd Edition, 2017
Bursts and bumps are defined in several ways depending on the organization concerned. For example, the U.S. Mine and Health Administration gives the definition: “Burst – An explosive breaking of coal or rock in a mine due to pressure; the sudden and violent failure of overstressed rock resulting in the instantaneous release of large amounts of accumulated energy where coal or rock is suddenly expelled from failed pillars. In coal mines they may or may not be accompanied by a copious discharge of methane, carbon dioxide, or coal dust; also called outburst; bounce; bump; rock burst.” The presence of methane and similar strata gases complicates the mechanics of bursts and bumps through the concept of effective stress that governs strength of permeable media. An “outburst” is a violent failure associated with a sudden expulsion of coal from an excavation wall that is accompanied by release of large amounts of methane. Similar events occur in some salt mines with the production of “pop corn” salt, a highly granulated form of failed material (salt).
Optimal selection of coal seam pressure-relief gas extraction technologies: a typical case of the Panyi Coal Mine, Huainan coalfield, China
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
Zheng Shang, Haifeng Wang, Yuanping Cheng, Bing Li, Jun Dong, Qingquan Liu
The method of mining a protective coal seam and performing methane pre-drainage in a pressure-relief coal seam can effectively eliminate the danger from gas outburst (Cheng, Yu, and Yuan 2004; Karacan et al. 2011). Most of the coal seams in China influenced by geological tectonic movement are considered to have developed into complex and soft structures (Cheng and Yu 2007). As a result, the permeability of the coal seams which is not more than 0.1 × 10−3μm2 (the lowest in the Beipiao coal field is 0.7 × 10−4μm2; the highest in the Fushun coal field is only 1.8 × 10−3μm2), are significantly lower than those in the San Juan and Black Warrior basin of the USA (Hu, Jiang, and Su 2000). Consequently, protective seam mining is the most effective method for achieving the safe and economic exploitation of an outburst coal seam (Dong et al. 2015). The coal seam located above the protective coal seam is called the upper protective coal seam, and the lower protective coal seam is located below the protected layer (Liu et al. 2010). Vertical cracks and delamination cracks in the protected layer will significantly increase the permeability of the overlying coal strata (Figure 1) (Karacan et al. 2006). In recent years, the main method for performing pressure-relief gas extraction in China is surface well drilling and net-like penetrating boreholes (NPB) extraction and depends on the different coal seams, gas occurrence, and geological conditions long-term exploration (Jin et al. 2016; Kong et al. 2014; Liu et al. 2011; Yuan 2013c).
Research on evaluation technology of gas anomaly zone in Xiadian Mine based on 3D seismic monitoring technology
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Man Wang, Yingwei Wang, Dongming Zhang
In the underground coal mining process, coal and gas outburst is a dynamic phenomenon of coal body that suddenly erupts a large amount of mixture of coal and gas from the interior of coal and rock mass to the excavation space in a short time (Hu and Wen 2013). It has caused huge impacts, causing serious damage to underground production equipment and roadway support, and even caused more serious gas explosion accidents (Qi and Dou 2008). At present, disasters such as coal and gas outburst have become one of the main factors affecting coal mine safety, which seriously restricts the safe and efficient production of mines. Statistical data show that coal and gas outburst are closely related to geological structure, and most of the prominent accidents occur in the vicinity of the tectonic belt (Zhang and Liu 2016). Therefore, geological structure is an important factor to induce gas outburst, rock burst and other disasters.
A rapid prediction technology for the outburst risk of coal uncovered in crosscuts and shafts and its application in the Panyi Coal Mine in Huainan, China
Published in Mining Technology, 2018
Yujia Chen, Xiaowei Li, Jun Tang, Dingding Yang, Chenglin Jiang
Coal and gas outbursts are serious mine disasters that threaten the safety of coal miners and production. Currently, nearly 40,000 coal and gas disasters occur around the world. Among these outbursts, nearly half occur in China (Lama and Bodziony 1998; Liu et al. 2008). With deep coal excavation development, coal seam outburst risks and their resultant disasters have become more and more severe (Cao et al. 2001). Due to a lack of effective outburst prediction and prevention measures, many European countries such as France, Belgium, Bulgaria, Czech, Hungary and Britain have shut down their outburst-prone mines (Harvey 2001; Fisne and Esen 2014). During coal mine construction or production, it is very important to accurately predict outburst risks before working in the mining face for the safety of coal miners and production, especially before coal uncovering in crosscut and shaft (CUCS). Due to the presence of barrier rocks, gas is barely released from coal seams. Thus, the outburst risk of coal seams represents the seam’s original state. Once an outburst occurs, serious consequences result. Overall, accurately predicting an outburst and taking specific prevention and control measures could avoid possible accidents and disasters and ensure safe and efficient coal production.