Monitoring and modelling of gas dynamics in multi-level longwall top coal caving of ultra-thick coal seams, Part II: Numerical modelling

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

doi:10.1016/j.coal.2015.04.009

Cited by 52 publications

(18 citation statements)

References 17 publications

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“…Rock mechanical properties used in the K.-50/C LTCC model (after Zavšek, 1993 andSi et al, 2015c more than100 m ahead of the face-line were filtered out. It was observed that the microseismic events concentrated in the area 40 m to 70 m ahead of the face-line (Fig.…”

Section: Tablementioning

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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Section: Tablementioning

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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“…With the rapid increase of computing capacity, numerical simulation continues to garner more attention in the field of engineering application. Si et al 21 used FLAC3D to simulate stress distribution in the extremely thick coal seams resulting from fully mechanized coal mining; they then used MATLAB to introduce the stress results to ECLIPSE300 to study gas migration. Understanding the respective influences of stresses on the overall permeability and flow pathways is critical to the development of a numerical model of the coupled hydromechanical process of fractured rocks in various fields of rock engineering.…”

Section: Introductionmentioning

confidence: 99%

A fluid‐solid coupling method for the simulation of gas transport in porous coal and rock media

Zhang

Liu

Zhao

et al. 2019

Energy Science & Engineering

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Understanding coal and rock permeability, and the corresponding influence on stress, is important in the field of energy development. In applied engineering, there is a tendency to employ three‐dimensional methods that are simpler, less time‐ and cost‐expensive, less computationally expensive, and larger scale. Thus, a numerical simulation fluid‐solid coupling method is proposed in this paper. The proposed numerical simulation method utilizes the stress‐permeability test results for elastic and plastic coal samples. The permeability models of the elastic and plastic coal samples under loading and unloading were obtained by fitting the experimental results and embedded them into FLAC3D software by using FISH language. The results of the uniaxial and triaxial flow simulations are consistent with the experimental results, thereby confirming the accuracy and feasibility of the numerical method proposed in this paper. This allows the permeability of the numerical reservoir model to be continuously updated according to the current stress level in the production process.

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“…The excavation of underground openings (including roadways and boreholes) has a significant effect on the in‐situ stress distribution of the surrounding coal . A wide zone of coal surrounding the roadway becomes broken after excavation, thus a large number of fractures may appear around the borehole due to the disturbance superposition of multiple excavations . These fractures expand and connect over time, and finally influence the sealing performance.…”

Section: Introductionmentioning

confidence: 99%

“…19 A wide zone of coal surrounding the roadway becomes broken after excavation, thus a large number of fractures may appear around the borehole due to the disturbance superposition of multiple excavations. 20 These fractures expand and connect over time, and finally influence the sealing performance. Furthermore, as the borehole acts as the methane flow channel, the failure of a borehole can significantly influence the drainage efficiency.…”

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confidence: 99%

An improved method for high‐efficiency coal mine methane drainage: Theoretical analysis and field verification

Liu

Zhang

Wang

et al. 2018

Energy Science & Engineering

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Degassing a coal seam with in‐seam boreholes is an important method for mitigating the gas hazards in the underground coal mine. However, the low strength of the outburst‐proven coal limits the borehole sealing performance and borehole space maintaining, and thus influences the drainage performance of in‐seam boreholes. This study was conducted to seek a method to improve the sealing performance and borehole space maintaining for high‐efficiency CMM drainage. A visco‐elastic plastic model involving the plastic softening and dilatancy features for soft coal was proposed, and the deformation, shrinkage, and fracture characteristics of the coal surrounded a borehole and a roadway were analyzed. An enormous amount of connective fractures generated in the failure zone and the plastic zone, and the plastic zone develops timely for the creep behavior of coal, which aggravates the difficulties of borehole sealing. A comprehensive approach including the theoretical method and the technical method was developed to determine the proper sealing depth which can significantly influence the sealing performance. The sieve tubes made of high‐density polyethylene has been used to maintain the borehole space during the scheduled pre‐drainage period. A series of field tests were conducted in an outburst‐proven coal seam to verify the feasibility of the comprehensive approach and the borehole space maintaining method. Field tests showed that the comprehensive approach to determine the proper sealing depth and the installing of sieve tubes to protect the borehole space can provide favorable conditions for maximum CMM pre‐drainage from outburst‐prone coal and maximum utilization of the in‐seam boreholes.

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Monitoring and modelling of gas dynamics in multi-level longwall top coal caving of ultra-thick coal seams, Part II: Numerical modelling

Cited by 52 publications

References 17 publications

Numerical modelling of microseismicity associated with longwall coal mining

Numerical modelling of microseismicity associated with longwall coal mining

A fluid‐solid coupling method for the simulation of gas transport in porous coal and rock media

An improved method for high‐efficiency coal mine methane drainage: Theoretical analysis and field verification

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