Influence of the stress state in a coal bump-prone deep coalbed: A case study

The effect of stress is one of the main natural factors that exerts a significant influence in coal bumps and rock bursts, especially in deep coalbeds. Sublevel caving is one of the methods that most influences this stress state and is therefore an extremely important parameter to consider when trying to improve mining conditions in mines with high methane content. This paper presents a practical case to illustrate the stress behavior of sub-vertical coalbeds in deep mines. The site study included two different locations, in two mines in the Riosa-Olloniego coalfield (Asturias, Spain) that are presently being mined by the sublevel caving method at a depth of around 1000 m. The research analyzed the influence that the caving of a particular panel of coal has on the upper and lower sublevels of the coalbed itself, as well as of neighboring coalbeds, with the aim of comparing different mining sequences. The site measurements carried out had two aims: to test the influence of adjacent workings on the 8th Coalbed and its coal-bearing strata and to verify the influence of the stress–strain change on the occurrence of coal bumps. Besides fulfilling these objectives, the work has also provided data for the calibration of possible numerical models that allow the simulation of present and future situations in the mine and has contributed to improving safety conditions of mining works in coal bump-prone deep coalbeds.