Estimation of near-wall rock mass stability when extracting exposed coal seam

Abstract

The paper considers assessing stability of the open pit southern wall when extracting exposed coal seam D₆. To assess the open pit southern wall stability when extracting exposed coal seams, modern research methods were used: the study of geology and analysis of the near-wall rock mass condition, creation of an observation station and monitoring, estimation of the southern near-wall rock mass stability, and analysis of the study findings. The pit southern wall is composed of clayey sediments up to 5 m thick, underlain by siltstone and mudstone up to 10-20 m thick, and a coal seam up to 5 m thick. Substantiation of the estimated strength characteristics of the rocks composing the open pit bench slopes, which determine the stress state of the slopes, arising under the effect of internal and external forces, has been performed. Instrumental observations produced by the station and the survey of fractures on the open pit wall enabled determining contours of the deformation zone and dimensions of the landslide prism. A geotechnical model of the near-wall rock mass was created, and stability assessment within the geological section along the line of maximum development depth was carried out. After implementing measures on surcharging slopes of the southern wall, the factor of safety amounts to: n_у =1.69−1.73 that indicates termination of the active phase of the wall deformation and confirms the wall stability.