Stability of roof structure and its control in steeply inclined coal seams

Li, Yongming; Wang, Zhaohui; Zhang, Jinwang

doi:10.1016/j.ijmst.2017.01.018

Cited by 53 publications

(19 citation statements)

References 4 publications

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“…e equation for σ y can be acquired by simultaneously calculating equations (9)- (11) and is given by…”

Section: Abutment Pressure Distribution Of Load-bearing Coalmentioning

confidence: 99%

“…By analysing the structural characteristics of coal and rock masses and fracture characteristics of the rocks surrounding the roadway, Wang et al [10] investigated the distribution and characteristics of zone divisions in fractured roadway surrounding rocks in steeply inclined, thick coal seams. Li et al [11] studied the stability of the roof structure and hydraulic supports with physical simulation and theoretical analysis, which shows that, with increased mining space, the caving angle of the roof strata above the main gate increases. e characteristics of the vertical and horizontal displacement of the roof strata demonstrate that caved blocks rotate around the lower hinged point of the roof structure, which may lead to sliding instability; however, current research into dynamic disasters of SICSs mainly concentrates on coal bursts in roadways while coal bursts in working faces of SICSs have not been of much concern.…”

Section: Introductionmentioning

confidence: 99%

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Coal Burst Induced by Horizontal Section Mining of a Steeply Inclined, Extra-Thick Coal Seam and Its Prevention: A Case Study from Yaojie No. 3 Coal Mine, China

Wang

2019

Shock and Vibration

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At present, coal bursts in working faces of steeply inclined coal seams (SICSs) have rarely been investigated, and current research focuses on the influences of roof breaking and instability of overlying structures in goaf on coal bursts; however, the stress state of coal masses in working faces being subjected to coal bursts is rarely researched. To overcome the above defects, a model for analysing stresses on coal masses in horizontal section of SICSs was established based on the coal burst that occurred in LW5521-20, Yaojie No. 3 Coal Mine, Lanzhou, Gansu Province, China. Moreover, the mechanism underpinning such a coal burst in SICSs was analysed based on the superposition mechanism of dynamic and static loads. The results show that the side abutment pressure near the roof and floor under the horizontal sections of SICSs is asymmetrically distributed in the vertical direction in which the peak of side abutment pressure near the roof is closer to the working face and therefore is taken as the source of static loads for coal bursts in working faces. When the superimposed dynamic load caused by hanging roof breaking and high static load borne in the coal masses is larger than the critical load for coal burst inception, a coal burst will occur. Furthermore, the superimposed dynamic load induced by coal bursts on the support and the initial static load on the supports are larger than their limiting load, which leads to support collapse and eventually causes dynamic failure of the working face. The coal burst in working faces in horizontal sections of SICSs can be prevented by using deep-hole presplit blasting in a hard roof, destress blasting in coal masses, and support optimisation of working faces, showing a favourable preventative effect.

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“…e equation for σ y can be acquired by simultaneously calculating equations (9)- (11) and is given by…”

Section: Abutment Pressure Distribution Of Load-bearing Coalmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Coal Burst Induced by Horizontal Section Mining of a Steeply Inclined, Extra-Thick Coal Seam and Its Prevention: A Case Study from Yaojie No. 3 Coal Mine, China

Wang

2019

Shock and Vibration

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“…These empirical criteria are also employed in the American coal mining industry, but with some modifications [15,16]. Factors affecting the disturbed zones such as in situ stress [17], physical properties of strata [18][19][20][21], inclination of the coal seam [7,22], and surface topography [12,23] have also been well studied.…”

Section: Introductionmentioning

confidence: 99%

A General Review on Longwall Mining-Induced Fractures in Near-Face Regions

Bai

2019

Geofluids

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It is believed that underground longwall mining usually produces fractures in the surrounding rocks. On the one hand, mining-induced fractures not only degrade the strength of the rock mass but also serve as main channels for fluids (e.g., water and methane). Fractures facilitate the failure of the rock mass and fluid inrush into working spaces. Therefore, mining-induced fractures are significant for the safety evaluation of underground structures and finding feasible solutions. On the other hand, the fractures are also beneficial for methane collection and coal fragmentation, which are essential for the successful operation of longwall top coal caving mining. Therefore, determining the characteristics of induced fractures is significant for underground longwall mining. From a global perspective, longwall mining-induced fractures in the overburden have been well studied, which improves the understanding of the mining pressure and ground control. However, induced fractures near the longwall face, which have more significant effects on mining activities, have not been summarized. The goal of this review paper is to provide a general summary of the current achievements in characterizing mining-induced fractures in near-face regions. The characteristics of mining-induced fractures in the coal wall, chain pillar, immediate roofs and top coal, and floors are reviewed and summarized. Remarks are made on the current progress of, fundamental problems with, and developments in methodologies for characterizing mining-induced fractures using methods such as field observations, small-scale laboratory tests, physical modeling, and numerical modeling. Based on a comprehensive analysis, the advantages and disadvantages of each method are discussed, and the ideal conditions for applying each of these methods are also recommended.

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“…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. To make the control of the surrounding rock more effective and improve the stability of the supports of the LTCC panel in steeply inclined coal seams, Wang et al (2017) and Li et al (2017) analyzed the forces imposed on the supports and proposed a new caving method drawing downward segment by segment while drawing upward in each segment. Based on a large number of creep experiments, Verma and Mishra (2015) investigated the time-dependent deformation behavior of immediate coal measures rock and explained the effect of timedependent deformation on roof stability.…”

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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Stability of roof structure and its control in steeply inclined coal seams

Cited by 53 publications

References 4 publications

Coal Burst Induced by Horizontal Section Mining of a Steeply Inclined, Extra-Thick Coal Seam and Its Prevention: A Case Study from Yaojie No. 3 Coal Mine, China

Coal Burst Induced by Horizontal Section Mining of a Steeply Inclined, Extra-Thick Coal Seam and Its Prevention: A Case Study from Yaojie No. 3 Coal Mine, China

A General Review on Longwall Mining-Induced Fractures in Near-Face Regions

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

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