Through the earth mine communications
Encyclopedia
Through-the-Earth signalling is a type of radio
signalling used in underground mines that uses low frequency waves to penetrate dirt and rock, which are opaque to higher-frequency conventional radio signals.
In mining these higher frequency signals can be relayed underground through various antennae
, repeater or mesh configurations, but communication is restricted to line of sight to these antenna and repeaters systems.
If the terrain makes a surface antenna impractical to install, then the antenna can be installed underground. But because the signal travels through rock, the antenna does not need to run into all parts of the mine to achieve mine wide signal coverage, thus minimizing the risk of damage during an incident.
at Moura
No. 4 Coal Mine in 1986 , and further developed after the Moura No. 2 Coal Mine explosion in 1994 where the need for a communication system to survive major incidents underground was identified in the enquiries into the disasters.
PED is a one-way text paging device, with widespread installations in Australia, and some installations at mines in the United States
, China
, Canada
and Sweden
. The best documented use of PED during a mine emergency is from the Willow Creek Mine Fire in 1998 in Utah
, where it was able to quickly alert miners underground of the need to evacuate the mine before toxic fumes from the fire filled the mine. Reports of this use can be seen on the Mine Safety & Health Administration (MSHA) web site at and .
the PED System is undergoing further development to provide two-way though the earth communication capability.
A recent demonstration in a US coal mine showed two-way TTE text messaging achieved at the deepest trials to date. Two-way signalling was achieved through 1,820 feet of overburden between the underground transceiver and the surface transceiver.
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
signalling used in underground mines that uses low frequency waves to penetrate dirt and rock, which are opaque to higher-frequency conventional radio signals.
In mining these higher frequency signals can be relayed underground through various antennae
Antenna (radio)
An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...
, repeater or mesh configurations, but communication is restricted to line of sight to these antenna and repeaters systems.
Overview
Through the earth transmission can overcome these restrictions in underground mines by using ultra low frequency signals, where the signals can travel through several hundred feet of rock strata. Hence an antenna can be located on the surface only at a mine site, and provide signal coverage to all parts of the underground mine. This is important in mining applications, particularly after any significant incident, such as fire or explosion, which would destroy much of the fixed communication infrastructure underground.If the terrain makes a surface antenna impractical to install, then the antenna can be installed underground. But because the signal travels through rock, the antenna does not need to run into all parts of the mine to achieve mine wide signal coverage, thus minimizing the risk of damage during an incident.
Personal emergency device
To date only one system has been successfully developed and deployed, and is known as the PED System, where PED is an acronym for Personal Emergency Device. Initially developed after a mining disaster in AustraliaAustralia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
at Moura
Moura, Queensland
Moura is a small town servicing the surrounding coal mining and rural activities. The town was first established in 1936 as a farming centre near the existing Moura Station.The town of Moura is located in Central Queensland, Australia...
No. 4 Coal Mine in 1986 , and further developed after the Moura No. 2 Coal Mine explosion in 1994 where the need for a communication system to survive major incidents underground was identified in the enquiries into the disasters.
PED is a one-way text paging device, with widespread installations in Australia, and some installations at mines in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, China
People's Republic of China
China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
and Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
. The best documented use of PED during a mine emergency is from the Willow Creek Mine Fire in 1998 in Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
, where it was able to quickly alert miners underground of the need to evacuate the mine before toxic fumes from the fire filled the mine. Reports of this use can be seen on the Mine Safety & Health Administration (MSHA) web site at and .
Development
On-going developments based on initial research undertaken in Australia by the Commonwealth Scientific Industrial Research Organisation (CSIRO) after the 1994 mine accident and given further impetus by the investigations into the Sago Mine disasterSago Mine disaster
The Sago Mine disaster was a coal mine explosion on January 2, 2006, in the Sago Mine in Sago, in Upshur County, West Virginia, USA, near the county seat of Buckhannon. The blast and collapse trapped 13 miners for nearly two days; one miner survived...
the PED System is undergoing further development to provide two-way though the earth communication capability.
A recent demonstration in a US coal mine showed two-way TTE text messaging achieved at the deepest trials to date. Two-way signalling was achieved through 1,820 feet of overburden between the underground transceiver and the surface transceiver.