Abstract
Roadway support and management of longwall panels in an island soft coal panel are always difficult work. In a test mine, stress distribution, deformation characteristic, and plastic zone distribution around the roadway and coal pillars in the development and mining periods were investigated with respect to the widths of different coal pillars using theoretical and simulation methods. The most reasonable width of coal pillars was comprehensively determined, and the field test was conducted successfully. The results show that a reasonable width of coal pillars is 7.0–8.2 m using the analytical method. The distribution of vertical stress in the coal pillars showed an asymmetric “double-hump” shape, in which the range of abutment pressure was about 26.0–43.0 m, and the roadway should be laid away from stress concentration. When the coal pillar width is 5.0–7.0 m, deformation of the roadway is half that with 8.0–10.0 m coal pillar in the development and mining period. The plastic zone in the surrounding rock firstly decreases and increases with increasing coal pillar width; the smallest range occurs with a coal pillar width of 5.0 m. Finally, a reasonable width for coal pillars in an island panel was determined to be 5.0 m. Industrial practice indicated that a coal pillar width of 5.0 m efficiently controlled deformation of the surrounding rock, which was an important basis for choosing the width of coal pillars around gob-side entries in island longwall panels with similar geological conditions.
Highlights
Gateway support of the island longwall panel in the soft coal seam is always a difficult problem because of stress concentration, which leads to serious deformation and failure of the surrounding rock and threatens the safety production [1, 2]
The strata behavior is more severe in the soft coal seam, so the influence of mining and side abutment pressure is more obvious in the island longwall panel inside of the soft coal seam, especially in the gob-side entry [3,4,5,6]
These studies are mostly based on soft rock roadway or ordinary island panel, respectively, and those aiming at the coal pillar width and surrounding rock control of the gobside entry in the island panel inside of the soft coal seam are less
Summary
Gateway support of the island longwall panel in the soft coal seam is always a difficult problem because of stress concentration, which leads to serious deformation and failure of the surrounding rock and threatens the safety production [1, 2]. A series of research on the stress and yield behavior of the coal pillar in the island longwall panel has been studied, including the study methods, the formula to calculate the reasonable width of the coal pillar, and the control mechanism of the surrounding rock [7,8,9,10,11,12]. These studies are mostly based on soft rock roadway or ordinary island panel, respectively, and those aiming at the coal pillar width and surrounding rock control of the gobside entry in the island panel inside of the soft coal seam are less. Concentrate, so the stress in the center of the pillar is higher than original rock stress, while the horizontal stress vertical to the axial direction of roadway is lower; 4 in every coal pillar with different widths, the range of where vertical stress is lower than original rock stress is 4.0–4.6 m, and in similar geological conditions, the total range of the fracture zone in the narrow coal pillar is 4.0–4.6 m, in which the fracture range of the roadway side is about 2.0–2.6 m, and that of the gob side is about 2.0 m
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