Correlation between coal and gas outburst risk and adsorption properties of coal seams

Abstract

Based on the Langmuir adsorption model, the adsorption constants of eighteen coal samples from the same coal mine with outburst risk, weak outburst risk, and non‐outburst risk were tested by high‐pressure capacity method under different temperature conditions. The results show that the adsorption constants a and b monotonically decrease with the increase in temperature. The relationship between a and temperature shows three stages: accelerated decreasing stage, decelerated decreasing stage, and stable stage. The b decreases with the increase in temperature also shows three stages, namely relative stability, slow decrease, and accelerated decrease. The a × b for the outburst coal seam decreases with increasing temperature, which is similar to b. The a × b for the weak and non‐outburst coal seams decreases with increasing temperature, which is similar to a. Furthermore, the a of the outburst coal seam decreases with the increase in temperature, and the decrease of b is the largest. The a of the weak and non‐outburst coal seams decreases with the increase in temperature, and the magnitude is relatively large. The b decreases slightly, with a smaller magnitude. The a × b of weak outburst seam is smaller than that of non‐outburst seam and is larger than that of outburst seam. The achievements can provide guiding significance for coal and gas outburst prevention and control.

Analysis of fractures of a hard rock specimen via unloading of central hole with different sectional shapes

“…Therefore, a large number of tunnels and chambers will be constructed and excavated in deep rockmass to meet the needs of underground engineering projects (Dammyr et al;Huang et al; Kang et al). Compared to the stress states of shallow buried depth, the mechanical characteristics of hard and brittle rocks at greater depth have been acknowledged to behave quite differently because of their complex stress states . Because a large amount of energy is stored in the hard rockmass, the excavation unloading of deep tunnels and chambers will lead to stress redistribution and concentration, which create favorable conditions for rock fracturing and instability .…”

“…Compared to the stress states of shallow buried depth, the mechanical characteristics of hard and brittle rocks at greater depth have been acknowledged to behave quite differently because of their complex stress states . Because a large amount of energy is stored in the hard rockmass, the excavation unloading of deep tunnels and chambers will lead to stress redistribution and concentration, which create favorable conditions for rock fracturing and instability . In situ measurements have shown extremely unconventional failure phenomena in deep mining and tunneling engineering such as slabbing, zonal disintegration, and rockburst, which are of great threats to safe and efficient underground construction and activity .…”

“…Much effort has been dedicated to understanding the instability and failure of surrounding rock of deep roadway after unloading . The mechanical response of rock around deep tunnels subjected to an unloading and loading mode should be quite different because of the disparate stress path between them . When an underground opening is excavated, the accumulated energy in the hard rock will be released and deformation and fracture will occur near excavation boundaries.…”

Applications of online integrated system for coal and gas outburst prediction: A case study of Xinjing Mine in Shanxi, China

“…Coal and gas outbursts are complex dynamic disasters, which, based on a comprehensive supposition, result from interactions among the structural mechanical properties of coal, ground stress, and gas pressure . In addition, coal and gas outbursts are closely related to geological structure, adsorption characteristics, and other factors . Through protracted and unremitting efforts, researchers from several countries have advanced various outburst prediction methods based on the understanding of outburst mechanisms.…”

Influence of water injection on the desorption characteristics of coalbed methane

“…15,16 As the permeability is often very low for complex coal structures, hydraulic methods that enable an increase in the water content and thus reduce the gas pressure of coal seams, including coal seam water injection, 17 hydraulic punching, and hydraulic extrusion, are the main techniques used to improve permeability before coal mining. [18][19][20] Field tests have shown that the gas emission from coal increases during the water injection process 18,[21][22][23] ; in contrast, experimental results have shown that an increase in the moisture content of coal has a significant inhibitory desorption effect on the adsorbed gas. 24,25 Thus, it is necessary to determine the influence of external water on the desorption character of the adsorbed coalbed methane in coal.…”