Optimization of roadway layout in ultra-close coal seams: A case study.
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ABSTRACT:
SUBMITTER: Wu G
PROVIDER: S-EPMC6248966 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Aiming at the problem of large deformation and difficulty in surrounding rock control of the top coal roadway in thick seam, theoretical analysis, theoretical analysis, numerical simulation, orthogonal matrix analysis and other methods were used to study the roof deformation and support parameter optimization of the top coal roadway in thick seam. Firstly, the structural model and roof mechanical model of the top coal roadway in thick seam were established, and the deformation coefficient TK was defined based on the relationship between curvature radius and bending moment, maximum bending moment and ultimate tensile strength of beam. According to the ratio of deformation rate between TK and beam to determine the roof deformation mode of top coal roadway, the discriminant conditions of roadway roof stability under two deformation conditions are obtained. Due to the characteristics of serious coal-rock fragmentation, large roof deformation, and integration of top coal and side coal. Therefore, the combined support method of "high prestressed long and short anchor cables" is proposed by double arch bearing structure control technology. Finally, based on the orthogonal matrix analysis method of supporting parameters optimization of the top coal roadway in thick seam, the analysis amount of supporting scheme is significantly reduced, the comprehensive evaluation of multi-factor and multi-supporting effect of roadway support is realized, and the optimal supporting scheme is obtained. Compared with the surrounding rock of the roadway without support, the deformation of the roof is reduced by 27.27%, the deformation of the two sides is reduced by 45.24%, and the tensile failure volume is reduced by 54.66%. The top coal roadway in thick seam has been effectively controlled, which provides guarantee for high yield and high efficiency of the mine.
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Project description:The intrusion of magmatic rocks into coal seams affects the coal quality and leads to unforeseen hazards in safety of the coal mines' production. This paper summarizes the mechanism of magmatic rocks intruding into coal seams, depicts the electromagnetic characteristics of the coal seams intruded by magmatic rocks, briefly describes the characteristics of transient electromagnetic method (TEM), and introduces the method of detection by TEM and the data processing steps. Then, the effectiveness of TEM in detecting the ranges of the coal seams intruded by magmatic rocks is theoretically analysed. It is observed that after the intrusion of magmatic rocks in the coal seams, the electromagnetic characteristics (secondary field potential and resistivity) will be dramatically affected, namely high secondary field potential and low resistivity. For experimental verification purposes, this study selects the test project of the Tongxin Minefield in the Datong Coalfield in Shanxi, China as an example, and the accuracy for the detection of the ranges of the coal seams intruded by magmatic rock using TEM is successfully verified.
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Project description:Fractures that develop in coal seams threaten safety in many ways, but they can be predicted using fracture parameters derived from seismic data. However, the post-stack split shear waves are difficult to thoroughly separate by Alford rotation due to wavefield mixing. We propose a method of predicting fractures in a coal seam using multi-component seismic data, which was applied to coal seam 13-1 of the Huainan coalfield, China. We employed the Alford rotation to separate the split PS-waves (P-to-S converted waves) and perform interlayer travel-time inversion of the fast shear waves using geophysical logs, rock-physics parameters, and tunnel-excavation information as constraints. However, post-stack wavefield mixing of the coal seam interfered with the Alford rotation of the real post-stack seismic data. Therefore, we only performed the Alford rotation on radial and transverse component post-stack sections to derive fracture azimuths, which were then applied to the pre-stack separation of the split PS-waves. Using joint PP- and PS-wave inversion, anisotropy parameters were derived for use in fracture prediction. Finally, we predicted unsafe mining areas with a high probability of coal and gas outbursts. The application results were verified by excavation data from the mine tunnels. Our method contributes to fracture prediction on coal mine safety.
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Project description:To study the influence of different factors on the cracking effect of the liquid CO2 phase transition, the mechanics of coal rock crack extension based on liquid CO2 phase change blast loading were studied. Through the application of simulation software to analyze the influence of coal seam physical parameters (in situ stress, gas pressure, modulus of elasticity and strength of coal) and blasting parameters (fracturing pore size and peak pressure of detonation)on the effect of liquid CO2 phase change cracking, the simulation results showed that the cracking effect of liquid CO2 phase change was positively correlated with the changes in gas pressure, elastic modulus, fracture hole diameter and peak vent pressure, negatively correlated with the variation in situ stress and compressive strength, and nearly independent of the tensile strength. In addition, by using Gray correlation analysis to analyze the influence degree of six main factors on the cracking effect, the calculation results showed that the effect of blasting parameters was greater than that of physical parameters. The main controlling factor that affected the blasting effect was the peak pressure of blasting release. By conducting comparative engineering trials with different blasting parameters, the test results showed that the crack effect of the coal seam was positively correlated with the change in fracture hole diameter and peak venting pressure, which was consistent with the results obtained from the simulation. The experimental results and simulation results for the effective radius of coal seam fracturing were basically consistent, with the error between the two types of results falling below 10%. Therefore, the reliability of the blasting numerical model was verified. In summary, the research results provide theoretical guidance for applying and promoting liquid CO2 fracturing technology in coal mines.
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Project description:The subsurface represents a largely unexplored frontier in microbiology. Here, coal seams present something of an oasis for microbial life, providing moisture, warmth, and abundant fossilized organic material. Microbes in coal seams are thought to syntrophically mobilize fossilized carbon from the geosphere to the biosphere. Despite the environmental and economic importance of this process, little is known about the microbial ecology of coal seams. In the current study, ecological succession and spatial niche partitioning are explored in three coal seam microbial communities. Scanning electron microscopic visualization and 16S rRNA sequencing track changes in microbial communities over time, revealing distinct attached and planktonic communities displaying patterns of ecological succession. Attachment to the coal surface is biofilm mediated on Surat coal, whereas microbes on Sydney and Gunnedah coal show different attachment processes. This study demonstrates that coal seam microbial communities undergo spatial niche partitioning during periods of succession as microbes colonize coal environments.
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Project description:Microbes in subsurface coal seams are responsible for the conversion of the organic matter in coal to methane, resulting in vast reserves of coal seam gas. This process is important from both environmental and economic perspectives as coal seam gas is rapidly becoming a popular fuel source worldwide and is a less carbon intensive fuel than coal. Despite the importance of this process, little is known about the roles of individual bacterial taxa in the microbial communities carrying out this process. Of particular interest is the role of members of the genus Pseudomonas, a typically aerobic taxa which is ubiquitous in coal seam microbial communities worldwide and which has been shown to be abundant at early time points in studies of ecological succession on coal. The current study performed aerobic isolations of coal seam microbial taxa generating ten facultative anaerobic isolates from three coal seam formation waters across eastern Australia. Subsequent genomic sequencing and phenotypic analysis revealed a range of ecological strategies and roles for these facultative anaerobes in biomass recycling, suggesting that this group of organisms is involved in the degradation of accumulated biomass in coal seams, funnelling nutrients back into the microbial communities degrading coal to methane.
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