Experimental and Theoretical Investigation of Overburden Failure Law of Fully Mechanized Work Face in Steep Coal Seam

Abstract

In this study, both theoretical analysis and similar simulation experiment are employed to investigate the overburden failure law of fully mechanized face in the steep coal seam. By establishing the mechanical model of inclined rock beam, the deflection equation of overlying strata beam is obtained. Based on the geological conditions of Xiangyong coal mine in Hunan Province of China, the laws of roof deformation and failure in steep coal seam are obtained by similar simulation experiments. The results showed that the roof deformation of the goaf is relatively large after the working face advances along the strike, and the deformation mainly occurs in the upper roof of the goaf. The backward gangue in the immediate roof fills the lower part of the goaf, which plays a supporting role in the lower part of the roof and floor. The roof fracture of goaf is located in the middle and upper parts of the working face, which is consistent with the results derived from the mechanical model. After the roof fracture, a “trapezoid” bending fracture area and the secondary stability system area is formed, which is composed of four areas: the lower falling and filling support area, the upper strata bending fracture area, the fracture extension area, and the roof bending sinking area.

Study of Top Coal Partition and Key Delayed-Action Region for Horizontal Sublevel Top Coal Caving in Deeply Inclined Seam

“…is model can also be extended by combining with strength criterion of complex stress condition to predict its different failure mechanism [30,31]. Moreover, in order to make a comprehensively understandable mechanism of progressive failure of deeply inclined seam, further research is required to determine stress distribution after roof breakage [20].…”

“…Before that, the key zone of top coal weakening should be found. Liao et al investigated the overburden failure law of fully mechanized face based on deflection equation of overlying strata beam [20]. Taking a cohesive element and considering the influence of geologic bedding plane around the roadway, the deformation and corresponding improved support scheme were analysed by Wu et al [21].…”

Study on Overburden Movement Deformation and Roof Breakage Law of Under-Protective Steeply Inclined Coal Seam Mining

“…In a certain period, the stress of the roof of the goaf will be reduced within a specific range, resulting in the expansion and deformation of the coal stratum, which makes the coal stratum move toward the goaf; the unloading and swelling deformation of overlying coal and rock mass can be reflected by the displacement and deformation of roof coal and rock strata to a certain extent [10,11]. Previous studies have shown that with a larger inclination angle of the coal seam, the tangential slip component along the rock layer increases, and the vertical pressure acting on the layer decreases so that the roof subsidence will gradually decrease [12,13]. When mining steeply inclined coal seams, the gangue falling in the goaf cannot stay in place in most cases due to its weight but slides down along the coal seam [14].…”