Mining Contract: Wireless Through-The-Earth Modeling and Support
This contract will determine the factors that most affect signal transmission and reception for through-the-earth (TTE) communication systems. This will be accomplished through modeling with validation at commercial mine sites, but it may still require transmission measurements from each TTE installation.
Contract Status & Impact
This contract is complete. To receive a copy of the final report, send a request to OMSHR@cdc.gov.
Since the passage of the Mine Improvement and New Emergency Response Act (MINER Act) of 2006, NIOSH has awarded several contracts toward the development of wireless communications and tracking equipment for use in the underground environment. As a result of this support, several through-the-earth (TTE) systems have successfully demonstrated communications through many hundreds of feet of overburden. At the time of this contract, there were no two-way TTE systems commercially available that met the permissibility requirements of the Mine Safety and Health Administration (MSHA). Many of the developers chose to first demonstrate the feasibility of their concept by using underground transmitters that exceed the power limits for permissibility, reducing the transmit power while attempting to maintain the communication link to the surface.
Data were collected at the CONSOL Energy Robinson Run coal mine in West Virginia and the McCoy coal mine in Kentucky. The purpose of the data collection was to demonstrate the overburden characterization tools developed under this contract. These tools allowed for the transmission of pre-recorded waveforms, reception of the waveforms, and then analysis of the received waveform to determine the strength of the received magnetic signal.
The equipment and software produced under this contract form a useful system to analyze the overburden of a mine. The waveforms produced were crafted to be usable even in noisy environments such as near the face of an operating coal mine. The data collected and the analysis performed on that data shows that there is greater attenuation as the waveform frequency increases. It is clear from the analytical results that the standard TTE signal propagation model does not encompass all of the physics relevant here. Using any single value of conductance will make the modeled graph intersect the measured graph at an arbitrary frequency point, but cannot change the slope of the modeled curve to match the measured data’s curve. Other physics that come into play with multiple layers of earth must be investigated to understand their role in TTE signal propagation.