Mining Program Area: Communications and Tracking
The Mine Improvement and New Emergency Response Act (MINER Act) requires mines to have wireless communications and electronic tracking systems in underground coal mines. The intent is to provide communications and location information between surface personnel and underground workers. The systems should be survivable and remain operational following a disaster to aid in self-escape and rescue operations.
As a result of the MINER Act, all underground coal mines now have some form of wireless communications and tracking (CT) systems installed. Because every radio has a limited transmission range, all CT technologies require some amount of underground infrastructure to transfer messages and information between the surface and underground. The CT equipment manufacturers have extensive knowledge about the capabilities of their equipment, especially when used on the surface, but much less knowledge about the impact of the mine environment on the performance of that equipment.
Radio signal propagation underground is very different than propagation on the surface. The mine environment plays a major role limiting the number of methods in which radio signals can propagate. At conventional cell phone frequencies, propagation is through the air, but the mine tunnels can act as a radio frequency (RF) guide for the signals. At lower frequencies, RF signals couple onto conductors within the entries, such as water pipes, power lines, trailing cables, pager phone wires, etc. At the lowest frequencies, it is possible to propagate RF signals directly through the overburden. OMSHR is investigating each of these three propagation mechanisms, categorized as ultra-high frequency (UHF), medium frequency (MF), and through-the-earth (TTE), respectively. Electronic tracking systems have similarities to the radio communications research, but some significant differences require tracking to have a separate research effort.
OMSHR will complete the RF propagation model development and validation in each of the three frequency bands. The propagation models will serve as inputs to a larger model that will quantitatively evaluate the survivability of the CT system and be able to perform “what if” evaluations of alternate CT technologies, installation configurations, and several disaster scenarios in a specific mine. Tracking research will identify systems with reduced infrastructure requirements that will likely increase survivability.
OMSHR has funded and continues to fund manufacturers to develop more advanced and potentially more survivable CT systems. OMSHR has assembled an experienced intramural CT research team supported by nationally recognized laboratories and universities and subject matter experts. The initial research focuses on developing computer models to predict radio signal attenuation and its dependency on geometric and electrical properties of the mine. The model predictions are validated by RF measurements performed in mines.
Survivability of CT systems is very dependent on the specific mine layout, the CT technology, the CT installation, and the type and extent of the disaster being considered. OMSHR is presently investigating methods to import a specific mine’s map and capture the three dimensional features of the entries. Eventually other software modules will permit configuring a CT system on the map and evaluating the impact of predefined disasters on the CT system performance. The results will be made available to CT manufacturers, mine owner/operators, regulators, and other stakeholders through publications, presentations, workshops, and OMSHR website materials.