Analysis of Deformation, Permeability and Energy Evolution Characteristics of Coal Mass Around Borehole After Excavation

Xue, Yi; Ranjith, P.G.; Dang, Faning; Jia, Lei; Wang, Songhe; Xia, Tongqiang; Gao, Yanan

doi:10.1007/s11053-020-09644-0

Cited by 62 publications

(40 citation statements)

References 37 publications

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“…With reference to the permeability test of coal samples [38][39][40][41][42][43], the permeability of coal samples before and after grouting was tested through a triaxial gas seepage experimental system of coal and rock masses. Test conditions and results are listed in Table 2.…”

Section: Experimental System Andmentioning

confidence: 99%

Grouting Fractured Coal Permeability Evolution Based on Industrial CT Scanning

Yao

Liu

et al. 2021

Geofluids

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Gas extraction from coal seams in China faces various middle-term and long-term problems, such as the poor sealing quality and low extraction rate. The mean gas extraction concentration is only 30%. Studying the flowing laws of the grout and fracture plugging mechanism is of important significance to improve the sealing quality and increase the gas extraction efficiency. For this reason, a new coal-based grouting material was prepared in this study, and its parameters such as viscosity were tested. Moreover, a grouting theoretical model with considerations of the flowing of the grout and coal fracture plugging by migration and deposition of slurry particles was constructed. The crack distribution before and after the grouting of fractured coal samples was scanned with an industrial CT, and the fracture distribution of coal samples was reconstructed using an independently compiled MATLAB program. Meanwhile, the variations of the coal permeability before and after the grouting were tested. On this basis, this study built a numerical calculation model of the grouting in fractured coal samples to simulate the leakage stoppage and permeability reduction mechanism of the coal-based sealing material grouting. Results demonstrate that (1) according to the experimental test results, the new coal-based grouting materials achieve a good fracture plugging effect, and the fractures in coal samples after the grouting are filled densely by the grouting particles. (2) According to the simulation results, the permeability of grouting coal samples declines quickly and then tends to be stable. The overall permeability of coal samples and the fracture permeability are decreased by 93.5% and more than 99.9% in average, respectively. (3) Influences of the grouting pressure on the permeability variation of coal samples were investigated through a numerical simulation. It was found that a reasonable grouting pressure for coal samples is about 0.3 MPa. (4) The numerical simulation reproduces the whole process of the grout flowing and the fracture filling. The variation laws of the diffusion and the permeability of the grout which are calculated through a numerical simulation agree well with the experimental results, which verifies the reasonability of the model. Research conclusions can provide important significance in theory and practice to disclose the leakage stoppage and the permeability reduction mechanism of the borehole grouting during the gas extraction and strengthen the sealing effects of extraction boreholes.

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Section: Experimental System Andmentioning

confidence: 99%

Grouting Fractured Coal Permeability Evolution Based on Industrial CT Scanning

Yao

Liu

et al. 2021

Geofluids

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“…The above research results are focus on the water inrush mechanism of collapse column in north China, where the water resource is the Ordovician limestone aquifer in floor of coal seam [16,17]. However, the water resource of collapse column in southwest China is the Yulongshan and Changxing limestone aquifer in roof of coal seam, which is different from the water inrush of collapse column in north China [18].…”

Section: Introductionmentioning

confidence: 99%

Evolution Mechanism of Water-Conducting Channel of Collapse Column in Karst Mining Area of Southwest China

et al. 2021

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There are many karst collapse columns in coal seam roof in the southern coal field in China, which are different from those in coal seam floor in the northern coal field, due to the stratum characteristics. The karst collapse column in coal seam roof tends to reactivate and conduct water and induce the serious water inrush disaster, when the karst collapse column communicates with the overlying aquifer. In order to reveal the evolution mechanism of water-conducting channel of collapse column in karst mining area of southwest China, the aquifers and water inflow rule in 1908 working face in Qianjin coal mine are analyzed. Besides, the particle size distribution and mineral component of collapse column are researched by the X-ray diffraction test and the screening method, which are the basis for researching the water inrush mechanism in karst collapse column. On this basis, the water inrush of roof collapse column under the influence of mining is researched by establishing the numerical calculation model with the UDEC numerical software. The results show that the water flowing into the 1908 working face comes from the Changxing formation aquifer and Yulongshan formation aquifer above the coal seam, and the proportion of coarse particles and fine particles in collapse column is 89.86% and 10.14%, respectively. With the advance of working face, the water-conducting channel connected the working face with the aquifer, or the surface is formed by collapse pits, karst caves, and collapse column. The research results can be treated as an important basis for the water-preserved mining in southern coal field in China.

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“…The Datong coal mining area is a typical dual system of coal seam in China, where the Jurassic and Carboniferous coal seams are mined simultaneously [1,2]. At present, the Jurassic coal mining is almost finished, and the Carboniferous 3-5# extra-thick coal seam is the key mining zone in the Tongxin mine [3,4]. The harmful water in the gob comes from rainfall, rivers, and the overlying aquifer.…”

Section: Introductionmentioning

confidence: 99%

Disastrous Mechanism of Water Discharge in Abandoned Gob above the Stope in Mining Extra-Thick Coal Seam

et al. 2021

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The Datong mining area is a typical double system coal seam mining area in China, where the Jurassic and Carboniferous coal seams are mined simultaneously. The upper Jurassic coal seam has been largely mined, leaving a large amount of gob area. Besides, a large amount of harmful water is accumulated. With the exploitation of the 3-5# extra-thick coal seam in the Carboniferous system, the scope of overburden damage is greatly increasing, and the mining fracture field is further developed. Once the mining-induced fractures connect with the overlying gob, it is easy to induce the water discharge disaster. With the mining geological conditions of the 8202 working face in the Tongxin coal mine as references, the disastrous mechanism of water discharge in the abandoned gob above the stope in the mining extra-thick coal seam is researched by numerical simulation with the UDEC numerical software, and the research results are obtained. The water in the overlying gob percolates through the mining-induced fractures in the higher key layer forming a “shower” seepage pattern. The water in the above gob converges in the key fracture channel, flowing into the working face. The seepage in the fractures in the high key stratum experiences the process of increase, decrease, and stabilization, related with the stretching and extrusion deformation between the high key stratum blocks. Compared with other fractures, the flow rates in the No.2 and No.4 fractures in the far field key lay are larger, because the fractures are in the tension state, forming the “saddle-shaped” flow pattern. The influencing distance of mining-induced seepage is about 80 m in front of the working face. The research results provide a guided reference for the prediction and prevention of water discharge disaster in an abandoned gob above the stope in a mining extra-thick coal seam.

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Analysis of Deformation, Permeability and Energy Evolution Characteristics of Coal Mass Around Borehole After Excavation

Cited by 62 publications

References 37 publications

Grouting Fractured Coal Permeability Evolution Based on Industrial CT Scanning

Grouting Fractured Coal Permeability Evolution Based on Industrial CT Scanning

Evolution Mechanism of Water-Conducting Channel of Collapse Column in Karst Mining Area of Southwest China

Disastrous Mechanism of Water Discharge in Abandoned Gob above the Stope in Mining Extra-Thick Coal Seam

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