Effect of the size distribution of granular top coal on the drawing mechanism in LTCC

Wang, Jiachen; Wei, Weijie; Zhang, Jinwang

doi:10.1007/s10035-019-0923-5

Cited by 29 publications

(10 citation statements)

References 15 publications

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“…Based on this, they concluded that the vertical force on the roof beam of the support would decrease during the coal drawing and the support advancement. Using the Ruilong coal mine as an engineering background, Wang et al [12] studied the drawing mechanism of loose top coal in different size distributions through the combination of theoretical analysis, numerical simulation and physical simulation. The study showed that as the weighted average particle size of the top coal increased, the volume of DB increased linearly and the maximum width of it increased non-linearly; as the weighted average particle size of the top coal increased, the top coal recovery ratio tended to increase and then decreased; high recoveries were achieved when the weighted average particle size of the top coal was in the range of 150-250 mm; and a relatively dispersed top coal particle size distribution and large standard deviations [13] were more favorable for the drawing of the top coal.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of Top Coal Drawing Evolution in Longwall Top Coal Caving by the Coupled Finite Difference Method-Discrete Element Method

et al. 2021

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In longwall top coal caving (LTCC), the resource recovery ratio of the working face is directly determined by the top coal recovery ratio. An investigation of the evolution of top coal drawing characteristics and revealing the evolution of top coal drawing parameters is necessary when providing guidance for caving parameter selection and improving the top coal recovery ratio. Based on in-situ measurements of the size distribution of caved top coal blocks in Wangjialing coal mine, a finite difference method (FDM)–discrete element method (DEM) coupled method was applied to establish a “continuous–discontinuous” numerical model and the process from the first coal drawing to the common coal drawing was simulated with 17 separate working face advances. The evolution of the drawing body (DB), loose body (LB), and top coal boundary (TCB) was obtained. The results show that, the evolution of parameters of DB such as shape and size, drawing amount, length and deflection angle of the long axis of the profile ellipsoid tended to decrease first, then increase, decrease again, and finally stabilise; the increment of the LB advance coal wall distance and the coal pillar distance was close to 0 m in the common coal drawing stage, while width increment of the LB was close to the drawing interval (0.865 m). The TCB formed after each coal drawing round was fitted based on the improved “Hook” function. The evolution of height and radius of curvature of TCB’s stagnation point was analysed. This was divided into three stages: the first (first to third drawing rounds) was the initial mining influence stage, the second (fourth to ninth drawing rounds) was the transitional caving stage, and the third (after tenth drawing round) was the common coal drawing stage.

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Section: Introductionmentioning

confidence: 99%

Numerical Investigation of Top Coal Drawing Evolution in Longwall Top Coal Caving by the Coupled Finite Difference Method-Discrete Element Method

et al. 2021

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“…LTCC has great applicability to seam thicknesses [3][4][5][6][7][8], seam dip angles [9][10][11][12], roof conditions [13,14], gangue seam thicknesses [15][16][17], and so on. It has been successfully used in different complex geological conditions, with a relatively high recovery ratio [18][19][20][21]. Compared with slicing mining, LTCC saves plenty of labor and material resources, such as equipment conveyance and roadway excavation, which have great economic advantages.…”

Section: Introductionmentioning

confidence: 99%

“…However, when SOSCT is applied in extrathick coal seams, the residual top coal between drawing bodies is large, leading to a low recovery ratio and poor drawing balance, which makes SOSCT no longer applicable. Contrarily, the multiopening sequential caving technology (MOSCT) can allow the large size top coal to flow out of SO, increasing the recovery ratio and advance velocity in the extrathick coal seams [18].…”

Section: Introductionmentioning

confidence: 99%

Optimization of Caving Technology in an Extrathick Seam with Longwall Top Coal Caving Mining

Yang

Wei

2021

Advances in Materials Science and Engineering

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The optimization of top coal caving technology is an efficient method to improve the recovery ratio in longwall top coal caving (LTCC). In extrathick coal seams, the conventional single-opening sequential caving technology (SOSCT) shows the following problems: low recovery ratio, high rock mixed ratio, and poor drawing balance. For these problems, this research verifies the applicability of multiopening caving technology (MOCT) in extrathick coal seams theoretically. However, different drawing sequences have a great effect on the drawing mechanism. Based on the progressive drawing sequence of cluster-group-support, this paper firstly proposes a systematic naming method for the top coal caving technology. Furthermore, an independent cluster-group caving technology (ICGCT) is given, meaning that all supports are divided into several clusters, a cluster is divided into several groups, and clusters extract top coal in positive order while groups are in reverse order in the drawing process. By establishing an experimental model by the discrete element method PFC2D, the drawing mechanism is investigated under different caving technologies. The results show that ICGCT significantly improves the recovery ratio of the panel and mainly increases the drawing volume of top coal in the middle and upper end of the panel. The shape of the top coal boundary reflects the drawing efficiency. Due to the effect of drawing sequence in ICGCT, the generation and disappearance processes of coal ridge greatly decrease the residual top coal in the middle of the panel. The drawing body shape has a direct influence on the recovery ratio. Multiple complete drawing bodies exist in ICGCT, and the dispersion coefficient of drawing volume changes periodically in the range of 0.5–1.7, which is conducive to the management of drawing processes. In addition, discussing ICGCT and the dependent cluster-group caving technology (DCGCT), it is found that the recovery ratio of DCGCT has a slight increase, which enlarges the maximum drawing range of top coal at both panel ends, shortening the total drawing time of the panel. In summary, ICGCT provides a new approach for improving the recovery ratio and drawing balance in LTCC with an extrathick coal seam.

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“…Close‐distance coal seams are often extracted following a downward mining sequence, during which the mining of the overlying coal seam is almost the same as mining of a single coal seam. However, the mining process of the underlying coal seam is affected by mining activity in the overlying coal seam.…”

Section: Introductionmentioning

confidence: 99%

Study on the movement characteristics of the overlying stratum and surrounding rock control in ultraclose coal seams: A case study

Zhu¹,

Yao²,

Xia³

et al. 2020

Energy Science & Engineering

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In Fucun Coal Mine, the average spacing between the 3upper coal seam (UCS) and 3lower coal seam (LCS) is only 6 m. In the process of mining upper coal, the lower roadway (LR), which is 60 m away from upper pillar, becomes unstable. In order to control the surrounding rock of lower roadway, a physical model experiment and a 3D numerical calculation were performed in this study. The results of physical similarity simulation experiment show that mining of longwall face in UCS will lead to fracturing of key layers at a high elevation (KLHE) far away from the coal seam. The expanded goaf area caused large‐scale fracturing and rotation of the KLHE, which resulted in significant strata pressure behavior in LR. The numerical calculation results show that the LR should be within 19 m of the coal pillar. Finally, a plan which includes a proper location and a supporting system was proposed. The feasibility of the proposed plan is verified by an industrial application.

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Effect of the size distribution of granular top coal on the drawing mechanism in LTCC

Cited by 29 publications

References 15 publications

Numerical Investigation of Top Coal Drawing Evolution in Longwall Top Coal Caving by the Coupled Finite Difference Method-Discrete Element Method

Numerical Investigation of Top Coal Drawing Evolution in Longwall Top Coal Caving by the Coupled Finite Difference Method-Discrete Element Method

Optimization of Caving Technology in an Extrathick Seam with Longwall Top Coal Caving Mining

Study on the movement characteristics of the overlying stratum and surrounding rock control in ultraclose coal seams: A case study

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