Geoelectric field response characteristics analysis of floor roadway surrounding rock fracture caused due to coal seam mining

Abstract

The fracture of rocks surrounding the floor roadway during the mining of the working face of a coal mine is a complicated spatiotemporal process due to the superimposed action of multiple stress fields on the surrounding rock mass. Using the surrounding rock of a floor roadway in the working face of the Huainan Pan’er Mine as the research subject, we conducted real-time monitoring using geoelectric field monitoring technology, and found the spatiotemporal response law of the geoelectric field in the process of regional rupture and damage of engineering rock masses under a complex stress field environment. The results show that (1) the time series response characteristics and spatial distribution of the geoelectric field signal are closely related to the stress distribution and damage evolution of the surrounding rock mass; (2) the rupture and damage degree of the goaf floor significantly increased when the working face was pushed through the monitoring area for 20–40 m. During this process, the excitation current dropped by 4–12 mA, and the self-potential pulse fluctuation amplitude was greater than 400 mV; (3) from the beginning of the monitoring process to the end of the monitoring, the self-potential in the damaged area decreased by 250 mV, and the self-potential in the mudstone layer below the damaged area increased by 140 mV. The electrons released into the environment around the damaged rock mass during the severe impact phase of mining did not flow back to the damaged area, and the positive charge in the damaged rock mass gradually accumulated in the complete rock mass in units of rock strata; (4) when superimposed and supported by anchor rod and cables, the bearing capacity of the shallow bearing circle of the roadway was enhanced, and the excitation current presented a step-like overall increase during mining of the working face with a small drop after every significant increase. This result is of significance in monitoring the evolutionary process of real-time failure of rock masses under complex stress environments using geoelectric field information and in improving the quality of geoelectric field monitoring technology testing applications in the future.