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October 1999
Volume 51    Issue 10

Longwall strata control and maintenance system -- A stethoscope for longwall mining

Mining Engineering, 1999, Vol. 51, No. 10, pp. 23-27
Park, D.W.; Deb, D.


ABSTRACT:
A recent international longwall census shows that panel widths and lengths are growing at the rates of 2% and 8% per year, respectively (Reid, 1997). According to the census, the average capacity of a two-leg shield is 647 t (713 st) in the United States and 764 t (842 st) in Australia, indicating a trend toward increasing longwall size. Due to the increase in panel size, production increases at a faster rate, but the growing number of ground-control problems causes numerous production delays. Installation of high-capacity shields may provide the necessary roof support, but information on the interaction between shields and the surrounding strata is needed to evaluate longwall stability and to forecast any forthcoming unusual events. Today, due to the advancement of microcomputer technology, every leg can be equipped with an electronic pressure sensor for monitoring pressure in real time. These data can be recorded and transferred every minute to the headgate computer (Park et al., 1992, 1997). If needed, the data-acquisition rate can be set higher, such as at every 10 or 20 seconds.


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