... conditions at this underground longwall mine: a microseismic monitoring network, a seismic tomography system and a longwall shield-leg pressure recording system. Results from the monitoring systems were correlated in an effort to determine whether the diverse information could be used synergistically...

... the rear over- hang is not broken off square with the face. In our case, many observations behind the operating longwall indicated that the rear of the roof block usually breaks at about a 35 degree angle. metals & mining specification gob shield lemniscate leg pressure fabrication shield...