AUGER MINING
Auger mining is usually associated with contour strip mining and is considered underground mining. With this method, the coal is removed by drilling auger holes from the last contour cut and extracting it in the same manner that shavings are produced by a carpenter’s bit. The cutting heads of some augers are as high as 2.5 metres. As each stem works its way into the coal seam, additional auger stems are added, so that hole depths of more than 60 to 100 metres are not uncommon. Problems of subsidence, water pollution and potential fires are associated with augering.
Encyclopaedia Britanica
Mining induced subsidence is when the earth collapses
when a pillar or near-surface underground tunnel collapse occurs.
