Failure Analysis of a Rear Wall Chock Shield for Longwall Face in Coal Mines

This investigation was primarily aimed to examine the probable causes of sudden failure of one of the rear shield chock for longwall face in a colliery. The rear shield was made of micro alloyed steel and a through thickness fracture was observed in the 63 mm rear shield plate. Preliminary visual examination, non-destructive evaluation including dye-penetrant and magnetic particle testing, evaluation of mechanical properties, detailed optical and scanning electron microscopic analysis were the necessary supplements to this investigation. Finally, a study on residual stress measurement and effect of pulsating load on structural integrity was carried out. The outcome of the investigation infers that improper welding caused adverse metallurgical and stress conditions leading to sudden failure of the rear shield plate.