Abstract
The absence of a key stratum during overburden rock movement is crucial to the mining pressure of fully mechanized coal mining faces. Using physical and numerical simulations, the 21304 mechanized mining in Daliuta and Huojitu coal mining faces 1−2 appeared twice during a pressure frame accident analysis. The results indicate that a lack of key overlying strata is crucial to the mining of lower coal seams, particularly for the upper sections of a single key stratum of coal. When the key stratum of the upper coal seam is absent, a stable masonry structure is formed after mining. It is easy to form stable stacked strata at the bottom of a coal seam. When developing gullies in deep terrains, the formation of the key stratum will be an upper rock fracture affected by the impact, resulting in a partial absence of the key stratum. When the key stratum is absent, the mining of upslope working faces and the probability of dynamic strata pressure increase with the overburden on the working face and mining of downslope faces. The face mine pressure development laws on the upper and lower coal seam mining were similar, mainly manifesting as “slope section >valley bottom section >back slope section.”
Highlights
In recent years, domestic and foreign experts and scholars have carried out a lot of research work on the movement rule of mining-induced overburden and the influence of key strata
Because the key layer of the overlying rock is affected by the change of stress distribution, and the shallowly buried coal seam distance is close to the surface, shallow seam mining under gullies is greatly influenced by the surface topography, and shallowly buried coal seams near the surface in valleys result in a lack of key strata, affecting the pressure of the fully mechanized working face
By analyzing the conditions of two intense pressures in the 1−2 coal of 21304 fully mechanized working face of the Huojitu coal mine, it was determined that when the main key stratum is present after mining in the upper coal seam, a stable masonry beam structure can withstand certain loads owing to the crushing of broken blocks
Summary
Domestic and foreign experts and scholars have carried out a lot of research work on the movement rule of mining-induced overburden and the influence of key strata. Because the key layer of the overlying rock is affected by the change of stress distribution, and the shallowly buried coal seam distance is close to the surface, shallow seam mining under gullies is greatly influenced by the surface topography, and shallowly buried coal seams near the surface in valleys result in a lack of key strata, affecting the pressure of the fully mechanized working face. A large area roof collapse violently occurred when the working face was pushed to 1875 m, and for its geomorphologic features are the middle position of the upper slope section of the gully, the pressure data of the support were 9874–1103 kN. Mining in the bottom section of the weighting average interval of 20.1 m occurs with an average length of 1.2 m. ere is pressure in the slope mining section average interval of
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