Following the blasting fatality on 17 December 2009, Landau Colliery
was forced to change from the blasting practices that had been
utilized since the start-up of the mine. Since then, attempts have been
made to optimize blasting results. The challenge is rooted to the
mining environment – during the early life of the mine, mining took
place in virgin areas, whereas currently mining is taking place in
areas overlying old underground bord and pillar workings. The
underground bord and pillar workings aggravate phenomena such as
spontaneous combustion, hot holes, and sinkholes. The 2009 fatality
was attributed to hot holes causing premature detonation. Landau
has been struggling with poor results from their overburden and coal
blasts; leading to poor fragmentation of overburden and the P1
parting that lies between the No.1 and No.2 coal seams.
An extensive literature survey was completed in order to identify
possible alternative solutions that could be evaluated for this unique
mining environment, which demands a high degree of caution during
mining to ensure factors such as dragline stability and personnel
safety. The literature survey confirmed that the previous blasting
technique, which was mainly characterized by air decking, was
indeed the more efficient, although it was deemed unsafe because of
the possibility of hot holes and the high sensitivity of detonators.
Potential modifications to the blasting technique were modelled
in a Microsoft Excel simulation that was available from the mine, and
pit visits were conducted in order to determine whether implementation
would be a problem. From the model it is evident that results
can be improved by changing the current burden and spacing ratio.
Visiting the pit revealed that the tie-in pattern and drilling inaccuracies
are contributing to problem areas.