Study on characteristics of EP responsing to coal mining

Abstract

Geophysical methods have been applied for monitoring and forecasting dynamic failure of coal rock in mining engineering widely. Previous researches indicate that electric potential (EP) signals are produced during the deformation and fracture process of coal rock under load, which are closely related to the stress state and damage evolution. On this base, the response of EP signal characteristics of coal seam to mining activity were tested and analyzed. The results showed, with the advancing of mining face, the stress state of coal mass near EP measuring point transited from the original stress zone to the stress concentration and distressed zones. It led to the increase of loading stress and damage degree of coal mass, resulting in the fluctuation and enhancement of EP strength. The response trend of EP exhibited great correspondence with the regular monitoring indexes. Besides, the phenomenon of periodic pressure also caused the abnormal response of EP. Furthermore, before the occurrence dynamic failure (mine tremor), the EP signals showed significant precursory warning characteristics. It was verified by monitoring the results of electromagnetic radiation (EMR). The study indicates the prospect of applying EP monitoring to evaluate the stress state and early warning of dynamic coal rock failure.