Drilling Method No. 1: Small heading, 60 to 80 ft. long. Two columns used in heading, with two drills on each. Drills on sub-bench and main bench mounted on tripods. +--------------------------------------------------+ | Per Round | +---------+---------+---------+----------+---------+ | | Total | No. of | Pounds | | | | Depth | Cubic | of | Advance | | | Drilled | Yards | Dynamite | | +---------+---------+---------+----------+---------+ | Heading | 140-155 | 18-21.6 | 93-131 | 5-6 | +---------+---------+---------+----------+---------+ | Bench | 110-120 | 53-60 | 76-97 | 3½-4 | +---------+---------+---------+----------+---------+ +---------+--------------------+-----------------------------+ | | Per Cubic Yard | Per linear Foot of Tunnel | | +---------+----------+-------+---------+-----------+ | | Linear | Pounds | Cubic | No. of | Pounds | | | Feet | of | Yards | Feet | of | | | Drilled | Dynamite | | Drilled | Dynamite | +---------+---------+----------+-------+---------+-----------+ | Heading | 8-9 | 5-6 | 3.6 | 29.-32 | 18-22 | +---------+---------+----------+-------+---------+-----------+ | Bench | 2 | 1.4-1.6 | 15.4 | 30.-31 | 21.5-24.6 | +---------+---------+----------+-------+---------+-----------+ | Total | 19 | 59.63 | 39.5-46.6 | +------------------------------+-------+---------+-----------+ | Per cubic yard, whole tunnel section | 3 to 33 | 2.1-2.5 | +--------------------------------------+---------+-----------+