Abstract
Gob-side entry retained with roadside filling (GER-RF) plays a key role in achieving coal mining without pillar and improving the coal resource recovery rate. Since there are few reports on the cyclic filling length of GER-RF, a method based on the stress difference method is proposed to determine the cyclic filling length of GER-RF. Firstly, a stability analysis mechanics model of the immediate roof above the roadside filling area was established, and then, the relationship between the roof stress distribution and the unsupported roof length was obtained by the stress difference method. According to the roof stability above the roadside filling area based on the relationship between the roof stress and its tensile strength, the maximum unsupported roof length and rational cyclic filling length were determined. Combined with the geological conditions of the 1103 thin coal seam working face of Heilong Coal Mine and the 1301 thick coal seam working face of Licun Coal Mine, the suggested method was applied to determine that the rational cyclic filling lengths were 2.4 m and 3.2 m, respectively. Field trial tests show that the suggested method can effectively control the surrounding rock deformation along with rational road-in support and roadside support and improve the filling and construction speed.
Highlights
(3) In view of different lengths of the lagging unsupported roof schemes, considering that the difference of each level of the length of the lagging unsupported roof is less than shearer cutting depth, we gradually increase the length of the lagging unsupported roof, calculate and solve, respectively, and obtain the corresponding maximum tensile stress
(4) e maximum tensile stress under each scheme is recorded, and the relevant maximum tensile stress is compared with the immediate roof tensile strength above the roadside filling area under this scheme, so as to determine whether the maximum tensile stress under this scheme exceeds the immediate roof tensile strength and determine the maximum length of the lagging unsupported roof in Gob-side entry retained with roadside filling (GER-RF)
Where L’ is the reasonable cyclic filling length in gob-side entry retained (GER)-RF, L3max is the maximum length of the lagging unsupported roof in GER-RF, and L5 is the minimum width of the pedestrian passage
Summary
(1) Firstly, according to the mining and geological conditions of the retained roadway, the mechanical model of immediate roof stability analysis above the roadside filling area in GER-RF was established and grid division was carried out. (5) According to the maximum length of the lagging unsupported roof in GER-RF and the minimum width of the pedestrian passage, we determine the reasonable cyclic filling length in GER-RF. It can be expressed as follows: L′ L3 max − L5,.
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