Document Type

Conference Paper

Publication Date


Publication Details

This conference paper was originally published as Bigby, D, MacAndrew, K and Hurt, K, Innovations in mine roadway stability monitoring using dual height and remote reading electronic telltales, in Aziz, N (ed), 10th Underground Coal Operators' Conference, University of Wollongong & the Australasian Institute of Mining and Metallurgy, 2010.


Rockbolting telltales are now an internationally established means of providing preemptive warnings of roof falls. The dual height telltale, providing an immediate visible measurement distinguishing between movement above and below the rockbolted height, is the most widespread version. The dual height telltale was first developed by British Coal in the early 1990's as rockbolting was introduced to replace steel arch support and the success of this support system in deep coal mines has been widely ascribed to the use of this safety device. Since its adoption, many permutations and improvements on the basic design have been developed and applied worldwide to suit different mining circumstances; for instance, triple height telltales are commonly used where a combination of roofbolts and longer tendons are installed at the face of the heading. The choice of appropriate movement action levels is vital for safety. Experience has also shown that systematic management of the application of the telltale warning system is required to ensure that appropriate action (usually the installation of additional support) is taken in time when action levels are exceeded. In Australia, this is exemplified in the TARP approach. Another major development has been an intrinsically safe remote reading dual height telltale system which allows up to 100 electronic telltales to be connected with a twin core cable and read, using either a portable readout, from the end of the roadway, or a surface PC via a telephone cable connection. In the latter configuration, a real time display of roof condition is obtained whilst retaining the immediate visual indication underground. A recent development is the “Autowarning” telltale. This provides a warning of impending goafing in depillaring operations via high visibility, flashing LEDs. The paper describes these and other telltale developments and provides case histories of their application worldwide, including UK, India, and USA.