Safety comparison of coal bunker construction meth

2022-09-23
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Safety comparison of coal bunker construction methods in mining areas

1.1 raise shaft construction method

for a long time, ordinary raise shaft method and single concrete support have been used in the construction of vertical coal bunker in coal mine. Zhuxianzhuang mine has also applied this method to the construction of coal bunker for many years, and there are many shortcomings:

(1) single concrete support by the raise shaft method. First, the small raise shaft is excavated and supported by wooden cribs, and then the arch back plate is used for temporary support after painting a large section. The gross section of coal bunker construction is large, and the erection of temporary support technology is relatively complex, with many links. These temporary supports need to be removed one by one before permanent support, which requires a large amount of labor, The construction speed is slow

(2) because a single concrete support can not change the stress state of surrounding rock, it is a passive bearing support method. According to the practical experience of Zhuxianzhuang mine for many years and the characteristics of high ground pressure, in order to ensure that the coal bunker has sufficient support strength within its service life, it is necessary to increase the pouring thickness of concrete. The concrete pouring for the coal bunker wall of Zhuxianzhuang mine is generally about 500mm, which not only increases the workload, but also increases the cost

(3) after driving the small raise shaft from bottom to top, it is not conducive to safe construction and quality

(4) before the construction of permanent support, it is necessary to remove the temporary support materials and increase the production environment, which ranks first among the seven national high-tech industrial bases of new material industry in China, which is not conducive to safety, and the temporary support requires a large amount of wood and steel, which is not conducive to saving support and reducing consumption

1.2 "bolting and shotcreting + concrete" combined support method

the 107 coal bunker in the seventh mining area of Zhuxianzhuang Coal Mine is a vertical coal bunker with a net diameter of 3.5m, a gross diameter of 4.3m and a height of 27m. The upper entrance of the coal bunker is located in the 107 transportation uphill of the seventh mining area and the lower entrance is located in the belt conveyor lane of the seventh mining area

the coal bunker passes through gray white siltstone, fine sandstone, ten coal seams, medium sandstone, sandy mudstone, and there is a normal fault with a drop of 2m. The lithology is relatively broken and easy to fall

first use the drill to pre excavate a small hole with a diameter of 1.2m, and then brush it from top to bottom until the design gross section diameter is 4.3m. Use smooth blasting to control the molding, so as to minimize the damage of blasting to the surrounding rock and improve the flatness of the warehouse wall, which is conducive to anchoring. Anchor support shall be carried out in a timely manner after each brush cycle of 1m, and then shotcreting shall be carried out with a thickness of 50mm. After the anchor and shotcrete support is completed, the overall concrete pouring can be carried out from the bottom. 3. The machining before heat treatment, personnel up and down, formwork arch, pouring, etc. are all carried out on the standard scaffold for construction. The scaffold is connected with standard fasteners. The concrete grade shall not be less than 300 #, the unidirectional compressive strength shall not be less than 25MPa, and the pouring thickness shall be 400mm. All processes must be carried out according to the design requirements during pouring

2 bolt shotcrete support parameters and the action principle of combined support

211 determination of bolt parameters

bolt length is determined according to the empirical formula:

l = n (n +b/10)

l = 1.1 × (1.1 × 4.3/10) = 1.68 (m), and the length of anchor rod L = 1.8m

where, l is the length of anchor rod, m; N is the influence coefficient of surrounding rock stability, class IV surrounding rock n = 1.1; B is the diameter of the gross section of the coal bunker, M

bolt spacing: D ≤ 0.5L = 0.5 × 1.8 = 0.9 (m), taking d = 0.8m

the row spacing m of anchor rods is also taken as 0.8m

anchor rods are arranged in diamond shape

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