Mining Publication: Detection of Trapped Miner Electromagnetic Signals Above Coal Mines
This report assesses the expected detectability, on the surface above mines, of electromagnetic signals produced in the 630- to 3,030-hz frequency band by a rescue transmitter activated by miners trapped underground. The assessment is based on a statistical analysis of experimental signal and noise data taken at coal mine sites distributed over the U.S. underground coalfields. Regression analyses are performed to characterize the signal transmission behavior of overburdens as a function of depth and frequency. The predicted signal behavior is then combined with experimentally based distributions of the background noise, and aural detection characteristics of signals in noise, to generate curves of the expected probability of detection for trapped miner signals versus overburden depth and operating frequency. The implications of the results and associated recommendations are presented regarding the detectability of trapped miners, sensitivity analyses and confirmatory tests, and operational utilization considerations for the trapped miners and the search and rescue teams on the surface.