GROUND FAILURE UNDER INGERSOL-RAND T4 BLASTHOLE DRILLING. DRILL WAS COMPLETING 150 ANGLE HOLE, 5.75"" DIAMETER, APPROX. 40'DEPTH HIT VOID. DRILL HAMMER STUCK COMING UP & WHEN DRILLER ""PULLED"" ON THE HAMMER THE FACE GAVE WAY. 3-4 THOUSAND TONS OF LIMESTONE SLID OUT FROM UNDER RIG. DRILL LAY ON LEFT SIDE W/OPERATOR CAB UP.