Abstract
As the national energy strategy is to mine westward, the deep coal resources under the super-thick and weak cementation overburden in the western mining area will play a critical role in China’s sustainable economic growth. The super-thick and weak cementation overburden has weaker lithology, thicker strata, no large joints, bedding development, and better integrity. Therefore, its movement rule is inevitably different from that of the weak overburden and the middle hard overburden in Central China and Eastern China. However, lack of studies on the movement of the super-thick and weak cementation overburden has led to severe constraints for the large-scale exploitation of coal resources under the super-thick and weak cementation overburden in the western mining area. This study explored the surface movement rule and the influence of overburden characteristics on strata movement with field measurement and numerical simulation. The findings indicate that the surface reaches full mining and the subsidence coefficient is about 0.9 when D1 (width in the dip direction) and D3 (length in the strike direction) are 3 times H0 (the mean mining depth) or more. The strike mining degree has a certain influence on the surface movement law, the maximum difference of the surface subsidence coefficient is 0.35, and the maximum difference of the horizontal movement coefficient is 0.05. In addition, the control effect of the Zhidan group sandstone is stronger. Thus, its first breaking results in surface sinking in a fractured manner when D1 is about 1.3 times H0 and D3 is 3 times H0 or more. The above results can provide reference for the safe mining and control of the super-thick weak cementation overburden.
Highlights
As the national energy strategy is to mine westward, the deep coal resources under the super-thick and weak cementation overburden in the western mining area will play a critical role in China’s sustainable economic growth. e super-thick and weak cementation overburden has weaker lithology, thicker strata, no large joints, bedding development, and better integrity. erefore, its movement rule is inevitably different from that of the weak overburden and the middle hard overburden in Central China and Eastern China
The control effect of the Zhidan group sandstone is stronger. us, its first breaking results in surface sinking in a fractured manner when D1 is about 1.3 times H0 and D3 is 3 times H0 or more. e above results can provide reference for the safe mining and control of the super-thick weak cementation overburden
To study the movement rule of the super-thick and weak cementation overburden in the case of large-scale mining and to grasp the relationship between the mining degree and the surface subsidence coefficient, this paper firstly investigated the surface movement rule of the super-thick and weak cementation overburden in the case of single working face mining (Figure 6). e working face was 300 m in width
Summary
We know that both the Zhidan group sandstone and the Jurassic sandstone formations have a certain control effect to the overburden movement. With the mining of working faces 2201–2205, the difference between the maximum subsidence values of Models 1 and 3 was 190 mm, 650 mm, 1164 mm, 1817 mm, and 1742 mm, respectively It increased rapidly, which had a positive relationship with the rapid expansion of the plastic zone in the Zhidan group sandstone in Model 3. Based on the simulation results the plastic zone range of Model 2 was wider than that of Model 1 in the same mining degree. Ere was no significant difference between the plastic zone diffusion of Model 1 and Model 2 because only the spatial position of the thick sandstone in the strata was changed, and their relative sequence in the strata was not reversed. Erefore, the relative sequence of the strong-control and the secondary-control strata in the overburden directly determines the failure pattern of the overburden and is the main factor to affect the overburden movement. e relative spatial position of the strong-control and the secondary-control strata in the overburden has little influence on the failure pattern of the overburden and is the secondary factor to affect the overburden movement
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