Transactions of the American Society of Civil Engineers, vol. LXVIII, Sept. 1910 | Page 5

Heading | 310-320 | 63-71 | 215-257 | 8-9 | +---------+---------+---------+----------+---------+ | Bench | 190-210 | 89-100 | 107-155 | 8-9 | +---------+---------+---------+----------+---------+
+---------+--------------------+------------------------------+ | | Per Cubic Yard | Per linear Foot of Tunnel | | +---------+----------+-------+----------+-----------+ | | Linear | Pounds | Cubic | No. of | Pounds | | | Feet | of | Yards | Feet | of | | | Drilled | Dynamite | | Drilled | Dynamite | +---------+---------+----------+-------+----------+-----------+ | Heading | 4.5-5.1 | 3.4-5.7 | 7.9 | 35.6-45. | 26.9-45.0 | +---------+---------+----------+-------+----------+-----------+ | Bench | 1.9-2.2 | 1.2-1.7 | 11.1 | 21.1-24. | 13.3-18.9 | +---------+---------+----------+-------+----------+-----------+ | Total | 19 | 56.7-69. | 40.2-63.9 | +------------------------------+-------+----------+-----------+ | Per cubic yard, whole tunnel section | 3.-3.6 | 2.1-3.4 | +--------------------------------------+----------+-----------+
+---------------------------------------------------+------------+ | | Number | | Blasting Notes: | of Sticks | | | | | All holes of whole round are cleaned and loaded | | | before blasting is started | | | | | | First Round: 5-6 lift holes, 7 to 9 sticks each | 35 to 54 | | First row, sub-bench, 6 holes, 6 to 8 | | | sticks each | 36 to 48 | | | | | Second Round: Second row, sub-bench and widening | | | holes, 8 to 10 holes, 6 to 8 sticks each | 48 to 64 | | Stub holes | 10 to 20 | | | | | Bench: Total Sticks | 129 to 186 | | Total Pounds | 107 to 155 | | | | | Third Round: 8 cut holes, 7 sticks each, often | | | requires 3 to 4 charges | 112 to 224 | | Fourth Round: 8 holes, First side round, 5 to 7 | | | sticks each | 40 to 56 | | Fifth Round: 8 holes, Second side round, 5 to 7 | | | sticks each | 40 to 56 | | 2 dry holes 5 to 7 sticks each | 10 to 14 | | Sixth Round: 4 to 6 widening holes and dry holes, | | | 6 sticks each | 36 to 48 | | Stub holes | 20 to 30 | | | | | Heading: Total Sticks | 258 to 428 | | Total Pounds | 215 to 357 | +---------------------------------------------------+------------+
The average quantity of powder used on the whole work was about 2.9 lb. per cu. yd. The tables on the diagrams, Figs. 1, 2, 3, and 4, show that the quantity actually used in making the advance at the main working faces was about 2.5 lb. The difference is accounted for by the larger percentage of powder used for trimming the sides, breaking out the cross-passages between the tunnels, and the excavation of the ditches, the latter operation not being done until the concrete lining was about to be put in.
There was some time, too, during the earlier stages of the work, when it is believed that an excessive quantity of powder was used; for one or two months it ran up to 4 lb. per cu. yd.
[Illustration: Fig. 5. MUCK CAR USED AT WEEHAWKEN SHAFT]
The dynamite used was "Forcite." At first, both 40% and 60% were used, the 60% generally only for blasting the cut in the headings; during the latter part of the work, however, the 60% was used exclusively.
The rock as a rule broke very well, and only a comparatively small quantity could not be handled by the shovels without being broken up further by block-holing. In the sandstone the quantity of powder per cubic yard was much more than for any of the trap.
In drilling the Central Shaft, a 6-hole cut was made approximately on the center line, east and west, the enlargement requiring about 18 more holes, which were generally about 6 ft. deep, the average advance being about 4 ft. per day of 24 hours.
[Illustration: Fig. 6. PROGRESS PROFILES OF NORTH AND SOUTH TUNNELS SHOWING MONTHLY EXCAVATION]
The drills were run by steam until a depth of about 150 ft. had been reached, air from the plant at Hackensack being available after that time. Four drills were used most of the time, and six later when air was available. This work was done entirely by the John Shields Construction Company, and a depth of 205 ft. was sunk in 6 months (from July 15th, 1905, to January 15th, 1906). A derrick was used for hoisting and lowering men and tools during the sinking, elevators being put in later.
[Illustration: PLATE XXIII.]
Drilling Data.--During the progress of the work, both general and detailed observations were made of the drilling, the results of which are shown in the tables. Table 1 has been compiled from the records as platted daily on the chart from the inspectors' reports, as shown by Plate XXIII, and