METHOD OF PREPARING BLOCK BOTTOM Russian patent published in 2001 - IPC

FIELD: mining industry; applicable in underground mineral mining. SUBSTANCE: method of block preparation includes driving of haulage ways, draw holes with slopes and receiving ports located in staggered manner; drilling of holes round draw holes over circumferences; loading and short-delay blasting of explosives with formation of pull holes. Pull hole is of semitruncated cone shape with vertical wall on side of haulage way. In this case, pull holes of underlying horizon are displaced with respect to overlaying horizon through value determined by formula A = Kd x Bdh, m, where A is value of displacement of pull holes of underlying horizon with respect of overlying horizon, m; Kd is coefficient of displacement ensuring variation of velocity of ore flows in vertical plane of block and is taken depending on mining system within 0.4-0.6; Bdh is distance between draw holes in row and between rows in block, m. EFFECT: reduced consumption of explosives for elimination of overhanging rock, higher stability of discharge and haulage workings and increased safety of mining. 3 cl