Monitoring and modelling of gas dynamics in multi-level longwall top coal caving of ultra-thick coal seams, part I: Borehole measurements and a conceptual model for gas emission zones

Si, Guangyao; Jamnikar, Sergej; Lazar, Jerneja; Shi, Ji‐Quan; Durucan, Şevket; Korre, Anna; Zavšek, Simon

doi:10.1016/j.coal.2015.04.008

Cited by 66 publications

(30 citation statements)

References 19 publications

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“…A conceptual gas emission model proposed by the authors (Si et al, 2015a) also suggested that, a relatively strong xylite-rich zone forming a barrier in front of a high gas content but relatively weaker detrite-rich zone may be the cause of increased gas emissions or gas outbursts at the mine. A detailed analysis of the spatial concentration of the microseismic events and gas emission rates described in this manuscript provides further evidence towards this conceptualisation.…”

Section: Discussionmentioning

confidence: 99%

“…Its matrix is fine-detrital, dark brownish in colour (Si et al, 2015a). Geomechanical tests on core samples from the drilling of underground boreholes at Coal Mine Velenje suggested that the lignite is highly heterogeneous and can vary significantly, even within a single borehole.…”

Section: The Field Monitoring Site At Coal Mine Velenjementioning

confidence: 99%

“…The tomograms shown in the above figures support these hypotheses. According to the borehole gas pressure and concentration measurements conducted at Coal Mine Velenje (Si et al, 2015a), the coal seam from around 40 m to 70 m ahead of the face-line experiences peak abutment stresses and prefailure cracks are initiated. With the longwall face 47 metres from the tomography zone, the area nearest to the face-line in the NW half of the panel has the lowest P-wave velocities, suggesting the fracturing of the coal under extreme abutment stresses.…”

Section: Analysis Of P-wave Velocity Tomogramsmentioning

confidence: 99%

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Seismic monitoring and analysis of excessive gas emissions in heterogeneous coal seams

Durucan

Jamnikar

et al. 2015

International Journal of Coal Geology

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Uncontrolled and excessive gas emissions pose a serious threat to safety in underground coal mining. In a recently completed research project, a suite of monitoring techniques were employed to assess the dynamic response of the coal seam being mined to longwall face advance at Coal Mine Velenje in Slovenia. Together with continuous monitoring of gas emissions, two seismic tomography measurement campaigns and a microseismic monitoring programme were implemented at one longwall top coal caving panel. Over 2,000 microseismic events were recorded during a period of four months. Over the same period, there also was a recorded episode of relatively high gas emission in the same longwall district. In this paper, a detailed analysis of the processed microseismic data collected during the same monitoring period is presented. Specifically, the analysis includes the spatial distribution of the microseismic events with respect to the longwall face advance, the magnitude of the energy released per week and its temporal evolution. Examination of the spatial distribution of the recorded microseismic events has shown that most of the microseismic activity occurred ahead of the advancing face. Furthermore, the analysis of the gas emission and microseismic monitoring data has suggested that there is a direct correlation between microseismicity and gas emission rate, and that gas emission rate tends to reach a peak when seismic energy increases dramatically. It is believed that localised stress concentration over a relatively strong xylite-rich zone and its eventual failure, which was also identified by the seismic tomography measurements, may have triggered the heightened microseismic activity and the excessive gas emission episode experienced at the longwall panel monitored.

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Section: Discussionmentioning

confidence: 99%

Section: The Field Monitoring Site At Coal Mine Velenjementioning

confidence: 99%

Section: Analysis Of P-wave Velocity Tomogramsmentioning

confidence: 99%

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Seismic monitoring and analysis of excessive gas emissions in heterogeneous coal seams

Durucan

Jamnikar

et al. 2015

International Journal of Coal Geology

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“…Specifically, the entire coal deposit is divided into a number of levels ranging from 10 to 20 m in thickness, and extracted sequentially from the top to the bottom. At each level, the lower section of the seam (3-4 m in thickness) is cut by a shearer under the hydraulic supports, and the top coal (7-17 m in thickness) is allowed to cave by gravity and be recovered in front of the supports (Si et al, 2015b). During coal extraction, the extending canopy is collapsed and the top coal is caved after several cuts at the face, allowing for a steady face advance.…”

Section: Analysis Of Mining-induced Microseismic Events At Coal Mine mentioning

confidence: 99%

Numerical modelling of microseismicity associated with longwall coal mining

Cao

Shi

et al. 2018

International Journal of Coal Geology

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A B S T R A C TMicroseismicity has long been a precursor for underground mining hazards such as rockbursts and coal and gas outbursts. In this research, a methodology combining deterministic stress and failure analysis and stochastic fracture slip evaluation, based upon the widely accepted fracture slip seismicity-generation mechanism, has been developed to simulate microseismic events induced by longwall mining. Using the built-in DFN facility in FLAC 3D, discrete fractures following a power law size distribution are distributed throughout a 3D continuum model in a probabilistic way to account for the stochastic nature of microseismicity. The DFN-based modelling approach developed was adopted to simulate the evolution of microseismicity induced by the progressive face advance in a longwall top coal caving (LTCC) panel at Coal Mine Velenje, Slovenia. At each excavation step, global stress and failure analysis with reference to the strain-softening post-failure behaviour characteristic of coal, and fracture slip evaluation for microseismicity are conducted sequentially. The model findings are compared to the microseismic event data recorded during a long-term field monitoring campaign conducted at the same LTCC panel. It was found that the released energy and frequency-magnitude distribution of microseismicity are associated with the slipped fracture sizes and fracture size distribution. These features for recorded microseismic events were fairly constant until a xylite rich heterogeneous zone ahead of the working face was approached, which indicates that fractures within the extracted coal seam follow the same size distribution. The features obtained from modelled microseismic events were consistent over the production period, and matched well the field observations. Furthermore, the model results indicate that the power law fracture size distribution can be used to model longwall-mining-induced microseismicity. This model provides a unique prospective to understand longwall coal mining-induced microseismicity and lays a foundation to predict microseismicity, or even rockburst potential in specific geological realisations.

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“…Advancements in mining technology and equipment have made fully-mechanized top coal caving (FMTCC) an important mining technique that can ensure safe and efficient production in mines with suitable conditions [1][2][3][4][5]. Using various methods, scholars have conducted systematic and in-depth research on the overburden movement and strata behavior induced by FMTCC in different conditions.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of Strata Behavior during Thick Seam Mining by Fully-Mechanized Top Coal Caving in a Loess-Covered Gullied Region

Wang

Zhang

et al. 2017

Minerals

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This study systematically investigates the overburden movement and strata behavior at a fully-mechanized top coal caving (FMTCC) face in a thick coal seam in a loess-covered gullied region by field measurement and theoretical analysis. A comparative analysis was performed to examine how the attitude of surface gullies and the structure of overburden affect face support resistance. The characteristics and evolution mechanism of strata behavior during FMTCC under gully slopes in a loess-covered gullied region were discovered through a mechanical analysis of the roof structure and a comparison to the mining of a typical shallow seam under gully slopes. The study found that as the FMTCC face advanced, the strata behavior initiated in the middle part of the face and then continued to both ends, and its intensity was higher in the middle part than in the upper and lower parts. During mining under gullies, the increases in support resistance were generally less than 5% (except for the maximum increases of 7-9%), indicating that the occurrence of gullies on the surface had little influence on the strata behavior at the FMTCC face. Due to the increased burial depth and the number of key strata, the roof at the FMTCC face under gullies formed a stable load-bearing structure called a voussoir beam, which was the key difference from the strata behavior characteristics in the shallow mine under gullies.

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Monitoring and modelling of gas dynamics in multi-level longwall top coal caving of ultra-thick coal seams, part I: Borehole measurements and a conceptual model for gas emission zones

Cited by 66 publications

References 19 publications

Seismic monitoring and analysis of excessive gas emissions in heterogeneous coal seams

Seismic monitoring and analysis of excessive gas emissions in heterogeneous coal seams

Numerical modelling of microseismicity associated with longwall coal mining

Characteristics of Strata Behavior during Thick Seam Mining by Fully-Mechanized Top Coal Caving in a Loess-Covered Gullied Region

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