Dip Angle Effect on the Main Roof First Fracture and Instability in a Fully‐Mechanized Workface of Steeply Dipping Coal Seams

Abstract

The fracture instability mechanism of the basic roof is the key to support selection and surrounding rock stability control, and it is also the guarantee of safe and efficient coal mining. By means of theoretical analysis and numerical calculation, the calculation model of basic roof of steeply dipping coal seams (SDCS) under linear load is established, the stress distribution expression of basic roof plate is deduced, the inclination effect of stress evolution of steeply dipping coal seams (SDCS) workface is analyzed, and the “sequential” weighting mechanism of workface is revealed. Based on the numerical simulation test, the evolution laws of vertical stress release and shear stress concentration of overlying strata in workface with different coal seam dip angles are obtained. The results show that there is shear stress arch in the overlying strata. With the increase of coal seam dip angle, the overlying strata are suddenly damaged under the action of shear stress. The roof is in the state of discontinuous movement due to its self-weight and overburden pressure. Support is affected by the discontinuous movement and moved along with the roof. The results of this study can be of theoretical reference to the control of SDCS.

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

“…Before the basic roof is broken, the basic roof and its overlying strata are supported by the surrounding coal walls. The basic roof is clamped by the coal wall and the overlying strata of the basic roof, and the coal wall and the overlying strata of the basic roof are overall layered structures in an extensive range [34]. Due to its limitations, in advancing the working face, the four sides of the basic roof can neither rotate nor sink, and only the elastic deformation of the suspended plate in the goaf can occur.…”

Study on roof breaking mechanism and support stability of steeply dipping seam and large mining height

“…The coal-forming environment of steeply dipping coal seams is complex, and safe and efficient mining is tough. In recent years, many experts, scholars, and engineers have carried out research and exploration on the problems of mine pressure behavior law (Wang et al, 2022; Yang et al, 2021; Tu et al, 2017), distribution characteristics and spatial distribution of surrounding rock stress (Dai et al, 2006; Wei et al, 2021; Wang et al, 2020; Wu et al, 2020a), asymmetric deformation and failure movement law of roof and floor strata and rock mass structure (Wu et al, 2021; Li et al, 2022; Luo et al, 2021, 2023; Chi et al, 2021; Shi et al, 1993; Li et al, 2022), surface subsidence caused by coal seam mining (Yin et al, 2001; Xie et al, 2020), coupling mechanism, and stability control of “support-surrounding rock” system (Hao et al, 2021; Wang et al, 2017; Xie et al, 2020; Zhang et al, 2023; Zhao et al, 2022; Yang et al, 2020; Wang et al, 2018), sliding and toppling mechanism of support and equipment (Chi et al, 2020; Zhang et al, 2008; Yang et al, 2018) and possible surrounding rock disasters. It has promoted the continuous progress of the theory and technology of longwall mining in steeply dipping coal seams, and greatly improved the poor safety of mining in steeply dipping coal seams.…”