Abstract
The concentration of abutment pressure acting on coal seams induced by mining is a key factor to trigger rock burst. Understanding of abutment pressure or stress concentration is fundamental in preventing and controlling rock burst. The influence on abutment pressure fluctuation caused by the inhomogeneity of coal seams needs to be considered, but it is difficult to obtain by the present usual ways such as acoustic transmission, electromagnetic wave transmission, etc. In this article, the relationship between the amount of cuttings drilled in a coal seam and stress level was analyzed by considering the effect of drilling cutting expansion, and the drilling cutting test was carried out in Xinglongzhuang Coal Mine, Shandong Energy Ltd. It is found that the amount of cuttings drilled is positively related to the degree of stress concentration in both the plastic fracture zone and elastic zone. The amount of drilling cuttings is closely related to the roof weighting. In addition, the irregular fluctuation of drilling cuttings is an approximate map of distribution of stress concentration because of the non-uniformity of cracks and other defects in the coal seam. In order to meet the need of rock burst prevention by accurate pressure relief in high-stress zones, enough boreholes are needed.
Highlights
Through tests of variation of drilling cuttings amount with different movement stages of the roof, which was performed in Xinglongzhuang Coal Mine, the following conclusions are obtained
It was found that the amount of cuttings drilled is positively related to the degree of stress concentration in both the plastic fracture zone and elastic zone
Drilling cuttings can be taken as an indication for verifying the distribution of abutment pressure and are helpful for pressure relief in mines
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Because of the complexity of different scale fissures or cracks in the coal seam structure and the influence of roof movement, the detection accuracy of abutment pressure and its changes by using vibration wave detection and online stress monitoring should be improved. Its principle is to drill small-diameter holes into coal; the amount of cuttings discharged through a hole per unit length is used to understand the stress concentration. This method was used first in the early 1960s in Germany [4]. In China, drilling cuttings began to be trialed for rock burst early warning in coal mines in 1985 [6,7]. This paper intends to analyze the relationship between drilling cuttings amount and the stress firstly, to investigate the relationship between drilling cuttings and abutment pressure distribution in different stages of roof movement as the coalface advances
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