Trial of small gateroad pillar in top coal caving longwall mining of large mining height

Li, Huamin; Peng, Syd S.; Li, Huigui; Xu, Yongxiang; Yuan, Ruifu; Yue, Shuaishuai; Li, Kun

doi:10.1016/j.ijmst.2015.11.022

Cited by 18 publications

(12 citation statements)

References 4 publications

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“…First, the retention of the coal pillars may lead to a serious waste of coal resources in the mining area; second, the tunneling speed may affect the continuation of working face recovery. With respect to coal pillar retention, to optimize the size of the retained pillar and maximize the recovery of coal resources, researchers have investigated the law of stress change and the pillar failure mechanism in the mining area using laboratory experiments, numerical calculations, and on-site monitoring [8][9][10][11][12][13]. Nonetheless, the problems existing in traditional longwall mining technology cannot be resolved by optimizing the size of the coal pillars, and nonpillar mining technology has become a research focus in the field of coal mining.…”

Section: Introductionmentioning

confidence: 99%

Stability Analysis and Monitoring Method for the Key Block Structure of the Basic Roof of Noncoal Pillar Mining with Automatically Formed Gob‐Side Entry

Liu

Wang

et al. 2019

Advances in Civil Engineering

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The key block of the basic roof is the main contributor to the structural stability of a roadway. Research on the stability of the key block structure is of great significance for the promotion of noncoal pillar mining with automatically formed gob-side entry (GEFANM) technology. This paper is set in the engineering context of the GEFANM experiment at the Ningtiaota Coal Mine. The study fully considered the differences in the gob roof caving on the roof-cutting-line side, and the range of rotation angles to maintain a stable key block was determined. Based on this range of rotation angles, the range of safe bulking coefficients of gangue was calculated. The bulking coefficient of the gangue on the gravel side of the roadway was used as the metric in a new monitoring method and in the calculation of the field parameters. The range of safe bulking coefficients was determined to be 1.40–1.37. Field monitoring was conducted to obtain the gangue bulking coefficient on the gravel side. Combining the roof and floor convergence data, when the bulking coefficient fell within the safe range, the convergence was 95–113 mm. In this stage, the key block structure was stable. When the gangue bulking coefficient fell outside the safe range, the convergence was larger, and cracks were observed. The key block may be vulnerable to instability. The results affirmed that the gangue bulking coefficient can be used as a monitoring metric to study the stability of key block structures.

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Section: Introductionmentioning

confidence: 99%

Stability Analysis and Monitoring Method for the Key Block Structure of the Basic Roof of Noncoal Pillar Mining with Automatically Formed Gob‐Side Entry

Liu

Wang

et al. 2019

Advances in Civil Engineering

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“…This, however, can lead to low coal recovery. To solve this problem, the gob-side entry approach has been proposed by researchers [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. As shown in Figure 2, it is a combination of a gateroad, pillar, and gob, which is a typical panel layout with slender pillar or artificial pillar or wall.…”

Section: Introductionmentioning

confidence: 99%

“…He suggested driving the gob-side entry along the gob with a 5 m slender pillar. Li [6] noted that a gob-side entry with a 6 m wide coal pillar based on numerical modeling was employed in LTCC in mining a 15 m thick coal retained as the entry for a future panel by constructing an artificial wall along the gob edge of the previous mined-out panel [3,4]. After excavation of a panel, the stress on the solid coal on the right (Figure 3) can be divided into four zones [2,5]: I-de-stressed yield zone, II-over-stressed plastic zone, III-over-stressed elastic zone, and IV-pre-mining vertical stress zone.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…He suggested driving the gob-side entry along the gob with a 5 m slender pillar. Li [6] noted that a gob-side entry with a 6 m wide coal pillar based on numerical modeling was employed in LTCC in mining a 15 m thick coal Yan [3] stated that the de-stressed zone occurs 0-7 m and the main roof will form the stable masonry structure to provide a low-stress environment for gob-side entry. He suggested driving the gob-side entry along the gob with a 5 m slender pillar.…”

Section: Introductionmentioning

confidence: 99%

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A New Gob-Side Entry Layout for Longwall Top Coal Caving

2018

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In China, gob-side entry is typically located one pillar-width (less than 5 m) away from the previously mined-out panel in a conventional longwall panel using top coal caving (LTCC). Design of gob-side entries is a challenge due to the complex dynamic loading process during their service life. A new gob-side entry (NGE) design practice is presented here for Zhenchengdi Colliery, which has many advantages. A theoretical analysis is presented followed by numerical modeling. The modeling included the double-yield constitutive model for gob behavior to analyze the stress environment for the gob-side entry with validation through field observations. The results indicate that pre-mining stress within gob occurred 51 m away from the gob edge. The NGE is located within a destressed zone in the entire panel system, which results in lower side abutment pressure for the adjacent panel to be mined. The stress concentration around the gob edge near the gob-side entry is relatively low (less than 0.1) compared with the other side of the gob. Field observations indicate that: (1) a simple support design, i.e., steel sets with wire mesh on the top, can maintain ground control and ventilation during active mining; (2) the periodic weighting interval is 9-12 m; (3) the length of the block "B" which "protects" the gob-side entry is 10-13 m; (4) stress distribution formula for the elevating section is derived; and (5) the roof pressure of the gob-side entry is much smaller than non-gob side entry and is smaller than the pre-mining stress. Deformation data of the gob-side entry shows that both roof-to-floor and rib-to-rib convergences are smaller than for the non-gob-side entry with an improved overall stress environment. Theoretical analysis, numerical modeling, and field observation are consistent, which validates the scientific foundations of the new technology.

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