Numerical simulation on fracturing behaviour of hard roofs at different levels during extra-thick coal seam mining

Gao, Rui; Huo, Bingjie; Xia, Hongchun; Meng, Xiuxia

doi:10.1098/rsos.191383

Cited by 13 publications

(8 citation statements)

References 24 publications

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“…Since the 150202 tailgate is excavated in a thick coal seam, the immediate floor and two ribs are composed of coal, the immediate roof is composed of mudstone, and the main roof is composed of limestone. Therefore, as the LTCC mining face advances, the stress release caused by the overhanging roof of the limestone will cause a significant floor heave and rib collapse (Gao et al, 2020; Verma and Singh, 2009), as shown in Figure 4(a) and (b).…”

Section: Case Analysismentioning

confidence: 99%

Mechanism of roof presplitting in nonpillar coal mining technology and its reasonable parameters in hard roof and longwall top-coal caving face

Wang

et al. 2022

Energy Exploration & Exploitation

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This article presents an integrated approach for theoretical analysis and numerical modeling to investigate the mechanism of roof presplitting and its reasonable parameters in the hard roof and longwall top-coal caving face. The test site is located in the city of Jinzhong, Shanxi Province, China. The theoretical analysis results indicated that when the presplitting angle remains constant, the tensile stress at the unpenetrated surface is approximately exponentially distributed with the presplitting height. When the presplitting height remains constant, the variation curve of tensile stress at the unpenetrated surface with the presplitting angle is parabolic. As the presplitting height increases, the presplitting angle required for the tensile stress at the unpenetrated face to exceed the ultimate tensile strength of limestone first increases and then decreases. The ground response of retained entry obtained with numerical modeling confirmed the theoretical analysis results. Meanwhile, numerical modeling results also showed that presplitting height affects the volume of the collapse gangues and the structure of the overlying strata above the retained entry. The presplitting angle is effective in reducing the frictional resistance between the collapse gangue and roof structure of retained entry. Moreover, based on the ground response of the retained entries, the reasonable parameters of the roof presplitting were determined at 17 m and 15°. The field application showed that reasonable roof presplitting parameters could achieve satisfactory effects at pressure relief and retained entry in the longwall top-coal caving panel. Furthermore, the proposed design principle of the roof presplitting technique can be applied to other projects.

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Section: Case Analysismentioning

confidence: 99%

Mechanism of roof presplitting in nonpillar coal mining technology and its reasonable parameters in hard roof and longwall top-coal caving face

Wang

et al. 2022

Energy Exploration & Exploitation

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“…The frame size of the physical model in the laboratory was 2:5 × 0:2 × 1:9 m (length × width × height). The geometric similitude ratio of the designed model was 150 : 1; the actual height of the model was 1.47 m, which simulated a height of 220 m. Materials including sand, calcium carbonate, and gypsum were used Table 3 shows the physical and mechanical parameters of the coal and rock mass [31]. According to the similarity ratio, the matching parameters of each rock formation in the model are shown in Table 3.…”

Section: Basic Parameters Of the Modelmentioning

confidence: 99%

Investigation on the Ground Pressure Induced by Hard Roof Fracturing at Different Layers during Extra Thick Coal Seam Mining

et al. 2020

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The fracturing of hard roofs in different layers would result in complex ground pressure on the working face, such as supports collapsed and severe roadway deformation. However, the mechanism of the ground pressure induced by hard roof fracturing in different layers is still unclear. In the paper, a physical model of a 20 m extrathick coal seam mined with hard roofs existing was established based on the physical simulation similarity criterion. The overburden fracturing structure, abutment stress distribution, and failure characteristics of the coal body were monitored by a noncontact strain measurement system and resistance strain gauges, to reveal the mechanism of ground pressure induced by hard roof fracturing. Furthermore, on-site measurement was used to monitor and analyze the ground pressure affected by hard roofs in different levels. The results provide a theoretical basis for the control of ground pressure in extrathick coal seam mining with hard roofs.

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“…Lu et al used the secondary developed FLAC3D simulation software to determine the target layer of surface fracturing [37]. Gao et al used the physical model and ABAQUS to research the characteristics of the overburden displacement and strata breaking strength after the vertical crack and horizontal crack existed in the high-level hard roof [38][39][40]. Based on the self-bearing of bulking rocks, the stability principle of the surrounding rock, and energy dissipation theories, Pan et al obtained the criteria for determining the fracturing horizon and thickness of the HHR [41].…”

Section: Introductionmentioning

confidence: 99%

Study on Movement Law of High-Position Thick and Hard Roof and Mine Earthquake Control by Ground Fracturing Technology

et al. 2022

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The field monitoring data showed that the fracture of high-position thick and hard roof (THR) was the main reason for the frequent occurrence of high-energy mine earthquake events ( magnitude > 2.0 ) in the no. 6 mining district of Dongtan coal mine. In order to study the fracture characteristics of high-level THR and seek a reasonable and effective control method, taking the 63up06 working face as the engineering background, the FLAC model was built to simulate the strata movement law before and after fracturing. The simulation results showed that the THR first breaking span was 340 m, the tensile failure runs through the whole THR, and the subsidence increased rapidly when THR reached the first breaking span. The THR breakage is related to the continuous upward transfer of horizontal compressive stress, which results in the concentration of horizontal compressive stress in THR. After ground fracturing, the first breaking span of THR decreased, and different fracturing positions have a great impact on the THR fracture form. When the fracturing position is close to the center of the first breaking span, there is no large cantilever breaking form in the THR, the THR breaks on both sides of the top and sinks along the hydraulic fracture in the middle, and the collapse degree is relatively uniform. Then, the fracturing test was carried out in the 63up06 working face, the results showed that during the first 400 m of the 63up06 working face mining after fracturing, 702 microseismic events occurred in total, including 12 high-energy vibration events which include 4 mine earthquakes of magnitude 2.0 and 8 mine earthquakes of magnitude 1.0-2.0. Compared with the adjacent working face, the quantity of high-energy mine earthquake events in the 63up06 working face has been significantly controlled.

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Numerical simulation on fracturing behaviour of hard roofs at different levels during extra-thick coal seam mining

Cited by 13 publications

References 24 publications

Mechanism of roof presplitting in nonpillar coal mining technology and its reasonable parameters in hard roof and longwall top-coal caving face

Mechanism of roof presplitting in nonpillar coal mining technology and its reasonable parameters in hard roof and longwall top-coal caving face

Investigation on the Ground Pressure Induced by Hard Roof Fracturing at Different Layers during Extra Thick Coal Seam Mining

Study on Movement Law of High-Position Thick and Hard Roof and Mine Earthquake Control by Ground Fracturing Technology

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