Transactions of the American Society of Civil Engineers, vol. LXVIII, Sept. 1910 | Page 3

of drilling and powder used, methods of blasting, etc., and on the progress profile, Fig. 6, is indicated those portions of the tunnels in which each method was used.
All the drills used throughout the work by Mr. Bradley were Rand No. 34 sluggers, with 3-5/8-in. cylinders, and the steel was that known as the "Black Diamond Brand," 1-3/8-in., octagon. It was used in 2, 4, 6, 8, 10, and 12-ft. lengths; toward the end of the work it was proposed to use 14-ft. lengths, but owing to some delay in delivery this length was never obtained. The starters, 18 to 24 in. long, were sharpened to 2? to 3-in. gauge, which was generally held up to depths of 6 ft.; then the gauge gradually decreased until it was 1? to 2? in. at the bottom of a 12-ft. hole. Frequently, as many as three or four starters were used in starting a hole, and generally two sharpenings were required for each 2 ft. drilled, after the first 6 ft. It is estimated that about ? in. of steel was used for each sharpening, and that there was an average of one sharpening for every foot drilled.
The total quantity of steel used up, lost, or scrapped on the whole work was almost exactly 1 ft. for each 10 cu. yd. excavated, equal to 1? in. of steel per yard, distributed approximately as follows:
Sharpening ? to 7/8 in. Other losses ? to 3/8 " --------------- Total 1? in. per cu. yd.
An "Ajax" drill sharpener was used, and proved very satisfactory. Rubber and cotton hose, covered with woven marlin, was used for the bench (3 in. inside diameter, in 50-ft. lengths), for drills (1 in. in diameter, in 25-ft. lengths), and for steam shovels (2? in. in diameter, in 50-ft. lengths). Hose coverings of wound marlin, and of woven marlin with spiral steel wire covering were tried, but were not satisfactory, owing to the unwinding of the marlin and the bending of the steel covering.
[Illustration: Fig. 1. {Drilling Method No. 1} CROSS-SECTION, LONGITUDINAL SECTION, PLAN]
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 | 3?-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 | +--------------------------------------+---------+-----------+
+---------------------------------------------------+------------+ | | Number | | Blasting Notes: | of Sticks | | +------------+ | Heading: First Round: 6 sticks, 60% in each cut | | | hole, cut generally blasted twice | 36 to 72 | | Second Round: 3 side holes each side, | | | 5 sticks, 40% ea. | 30 | | Third Round: Rest of side holes and dry | | | holes, 5 sticks, 40% each | 40 | | Stub holes, say | 5 to 15 | | +------------+ | Total Sticks | 111 to 157 | | +------------+ | Total Pounds | 93 to 131 | | +------------+ | Sub-bench: 4 widening holes; 2 to 3 sticks, | | | each, 40% | 10 to 12 | | 6 down holes; 5 to 7 sticks, each, 40% | 30 to 42 | | Bench: 6 holes; 6 to 8 sticks each, 40% | 36 to 48 | | Taking up bottom, average, say | 15 | | +------------+ | Total Sticks | 91 to 117 | | +------------+ | Total Pounds | 76 to 97 | +---------------------------------------------------+------------+
[Illustration: Fig. 2. CROSS-SECTION, LONGITUDINAL SECTION, PLAN]
Drilling Method, No. 2: Five drills in heading, mounted on three columns; the holes marked with a cross (X) were drilled with the drills on the center column.
+--------------------------------------------------+ | Per Round | +---------+---------+---------+----------+---------+ | | Total | No. of | Pounds | | | | Depth | Cubic | of | Advance | | | Drilled | Yards | Dynamite | | +---------+---------+---------+----------+---------+ | Heading | 190-220 | 35-42 | 134-196 | 6?-8 | +---------+---------+---------+----------+---------+ | Bench