Three-dimensional experimental study of loose top-coal drawing law for longwall top-coal caving mining technology

Wang, Jiachen; Zhang, Jinwang; Song, Zhengyang; Li, Zhaolong

doi:10.1016/j.jrmge.2015.03.010

Cited by 38 publications

(27 citation statements)

References 4 publications

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“…According to formula (18), the theoretical model of the shape of the top-coal drawing body parallel to the cross-section of the working face is shown in Figure 3…”

Section: Comparisonmentioning

confidence: 99%

“…Since 2000, low-level caving hydraulic support has been widely used in China. Through simulation tests, numerical analysis, and field observations, the theory of granular medium flow for topcoal drawing was proposed, which considered the influences of the CSL, shield beam, and tail beam on hydraulic support, and then, the boundary-body-ratio (BBR) research system was established to study the four factors of the coal-rock interface, top-coal drawing body, top-coal recovery rate, and rock-mixing rate (Wang and Fu 2002;Wang et al 2004Wang et al , 2015Wang et al , 2016a. Numerical simulation has also developed rapidly into an effective method for studying LTCC.…”

Section: Introductionmentioning

confidence: 99%

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Numerical Study of Reasonable Cycle Step Length for Longwall Top-coal Drawing in Extra-thick Coal Seams Based on the Particle-block Element Coupling Approach

Wang¹,

Li²,

Wang³

et al. 2020

Preprint

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The cycle step length (CSL) is a significant parameter for longwall top-coal drawing technology that remarkably affects the top-coal recovery rate and the rock-mixing rate, especially for extra-thick coal seams. In this study, a particle-block element coupling approach is performed to investigate a reasonable CSL for extra-thick coal seams. By comparing this approach to the Bergmark-Roos analytical result, the proposed numerical model is verified, showing good performance in modeling top-coal caving. A 2-D numerical model of hydraulic support considering the mechanical behavior of the legs is established, which can be used for modeling the interaction between the hydraulic support and the top coals during the top-coal drawing process. The top-coal recovery rate, the top-coal drawing body shape, and the evolution characteristics of the coal-rock interface under different CSL conditions are compared. In addition, the mechanism of the lost top coal affected by the CSL is revealed. The results show that the CSL of top-coal drawing has a significant effect on the morphology of the coal-rock interface and the mutual invasion of coal and rock, which is the primary reason for coal loss and further affects the top-coal recovery rate and the rock-mixing rate. It is suggested that the CSL should be 0.8 m when the top-coal thickness is 12 m.

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“…According to formula (18), the theoretical model of the shape of the top-coal drawing body parallel to the cross-section of the working face is shown in Figure 3…”

Section: Comparisonmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Numerical Study of Reasonable Cycle Step Length for Longwall Top-coal Drawing in Extra-thick Coal Seams Based on the Particle-block Element Coupling Approach

Wang¹,

Li²,

Wang³

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…To obtain the equation for the drawing body in the normal drawing stage in an inclined seam, it is necessary to know the polar coordinates of the tangent point A. According to Wang and Zhang (2015) and Wei et al (2018), the boundary of the top coal can be approximately described by a parabolic equation, which we shall assume here takes the form…”

Section: Equation For Drawing Bodymentioning

confidence: 99%

“…Most current research on LTCC in inclined seams concerns the top coal drawing mechanism, support stability, failure characteristics of overburden strata, and control of surrounding rock. Wang and Zhang (2015), Wang et al (2019), Zhang et al (2018a, b), and Song and Konietzky (2019) used the boundary-body-ratio (BBR) system, based on a series of laboratory experiments, field measurements and numerical calculations, to reveal the relationships among the drawing body and boundary of top coal and the recovery ratio in the LTCC panel. Yasitli and Unver (2005) and Unver and Yasitli (2006) studied the shape characteristics of the boundary and drawing body, and proposed that the uniformity of fracture of the top coal is directly related to the fluidity of top coal caving.…”

Section: Introductionmentioning

confidence: 99%

Theoretical description of drawing body shape in an inclined seam with longwall top coal caving mining

Wang

Wei

Zhang

2019

Int J Coal Sci Technol

Self Cite

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Understanding the characteristics of drawing body shape is essential for optimization of drawing parameters in longwall top coal caving mining. In this study, both physical experiments and theoretical analysis are employed to investigate these characteristics and derive a theoretical equation for the drawing body shape along the working face in an inclined seam. By analyzing the initial positions of drawn marked particles, the characteristics of the drawing body shape for different seam dip angles are obtained. It is shown that the drawing body of the top coal exhibits a shape-difference and volume-symmetry characteristic, on taking a vertical line through the center of support opening as the axis of symmetry, the shapes of the drawing body on the two sides of this axis are clearly different, but their volumes are equal. By establishing theoretical models of the drawing body in the initial drawing stage and the normal drawing stage, a theoretical equation for the drawing body in an inclined seam is proposed, which can accurately describe the characteristics of the drawing body shape. The shape characteristics and volume symmetry of the drawing body are further analyzed by comparing the results of theoretical calculations and numerical simulations. It is shown that one side of the drawing body is divided into two parts by an inflection point, with the lower part being a variation development area. This variation development area increases gradually with increasing seam dip angle, resulting in an asymmetry of the drawing body shape. However, the volume symmetry coefficient fluctuates around 1 for all values of the seam dip angle variation, and the volumes of the drawing body on the two sides are more or less equal as the variation development volume is more or less equal to the cut volume. Both theoretical calculations and numerical simulations confirm that the drawing body of the top coal exhibits the shape-difference and volume-symmetry characteristic.

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“…To illustrate the shape of the draw column, the marked particles were sketched along the original coordinates and the boundaries of the marked particles drawn were connected smoothly. The shape of the draw column was then outlined [18][19][20]. The morphological evolution of the draw column was as shown in Figure 4.…”

Section: Morphology Evolution Law For the Draw Column Interfacementioning

confidence: 99%

Correlation between ore particle flow pattern and velocity field through multiple drawpoints under the influence of a flexible barrier

Qin

Chen

et al. 2019

Open Geosciences

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By means of similar tests, the stope room is scaled and the process of multiple-drawpoint ore drawing under the influence of a flexible barrier is simulated by the marking particle method. Based on the experimental phenomena and data, the shape of the barrier, the draw column, and the numerical relations for the discharge between each drawpoint are analysed. The velocity equation for ore particles flowing through multiple drawpoints is established and the relationship between ore particle flow properties and velocity fields is found. Finally, the following results are derived: 1) For each layer, the morphology of marked particles is similar to that of vertical velocity. The particles are quasi-linear in the upper part of the model and wavy in the lower part. The amplitude increases with decreasing height. 2) The distribution of thirteen concentric points of horizontal velocity in each layer illustrate that the ore particles drawn from each drawpoint are from the centreline between it and the adjacent drawpoint. 3) The barrier and the marked particles are at the lowest sag points at the top of the number two and number six drawpoints (close to the model’s side wall) because of the combination of vertical velocity and horizontal velocity.

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Three-dimensional experimental study of loose top-coal drawing law for longwall top-coal caving mining technology

Cited by 38 publications

References 4 publications

Numerical Study of Reasonable Cycle Step Length for Longwall Top-coal Drawing in Extra-thick Coal Seams Based on the Particle-block Element Coupling Approach

Numerical Study of Reasonable Cycle Step Length for Longwall Top-coal Drawing in Extra-thick Coal Seams Based on the Particle-block Element Coupling Approach

Theoretical description of drawing body shape in an inclined seam with longwall top coal caving mining

Correlation between ore particle flow pattern and velocity field through multiple drawpoints under the influence of a flexible barrier

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