Transactions of the American Society of Civil Engineers, vol. LXVIII, Sept. 1910 | Page 6

described on page 113. Table 2 contains some data relating to the drilling in the headings.
The general results of these observations show that the average time the drills were "actually working" was 5.2 hours per shift, and that they were actually "hitting the rock" about half of this time, or about 2.5 hours per shift. The average depth drilled per hour, during the time the drills were "actually working," was 2.66 ft.
The "actual working time," as noted above, covers the period from the time the drills were first set up in the heading after blasting until they were taken down for the next blast; it does not include the time occupied in setting up or taking down, which would probably average 30 min. more per shift. It is believed that this figure will also apply very closely to drills working on the bench, though no actual observations were taken to determine this, on account of the irregularity with which they were worked.
The actual working time of the drills in the 736 shifts (7,360 hours) covered by Table 1, was 3,826 hours, or 5.2 hours per shift. The average depth drilled per yard, as shown in the last column of Table 1, agrees fairly well with the figures on the diagrams, Figs. 1, 2, 3, and 4.
Table 2 has been compiled from detailed timed observations of individual drilling of down holes in the bench, for periods of 7 or 8 hours each, in January, 1907. The work at that time was in fairly normal condition at all points.
The figures in the third column of Table 2 include the time required for moving from one hole to another, when this occurred during the observation, the time required for changing bits, oiling drills, etc., and all delays of all kinds. A close record of the delays was kept, and it was considered that, of the 93 hours, 48 min., in Table 2, the unnecessary delays amounted to 5 hours, 7 min., or about 5? per cent.
TABLE 1.
#S. Number of shifts covered by observations. #Hrs Average number of hours worked per shift. D/Hr Average depth drilled per hour per drill. D/Yd Average depth drilled per yard. Hack. Hackensack Whk. Weehawken CS Central Shaft
----------------+-----------+----+-----------+------+------+------ Method. | Date. | #S | Place. | #Hrs | D/Hr | D/Yd ----------------+-----------+----+-----------+------+------+------ {| Aug. '06 | 44 | Hack., N. | 5.69 | 2.78 | 10.1 {| Sept. '06 | 38 | " N. | 5.80 | 3.77 | 11.1 No. 1-- {| Aug. '06 | 43 | " S. | 5.60 | 2.89 | 9.1 4-drill {| Sept. '06 | 36 | " S. | 6.18 | 2.65 | 8.7 {| Jan. '07 | 16 | CS E. N. | 5.99 | 2.99 | 8.2 {| Jan. '07 | 20 | " S. | 6.05 | 2.9 | 7.1 {| Apr. '07 | 48 | CS W. N. | 4.92 | 3.3 | 6.7 {| Apr. '07 | 48 | " S. | 5.00 | 3.2 | 7.7 | | | | | | {| Dec. '06 | 54 | Whk., N. | 4.95 | 2.16 | 4.52 Nos. 2 and 3-- {| Dec. '06 | 54 | " S. | 5.23 | 2.14 | 4.54 5-drill {| Dec. '06 | 52 | Hack., N. | 5.03 | 2.2 | 5.77 {| Dec. '06 | 54 | " S. | 5.90 | 1.82 | 5.67 | | | | | | No. 4-- {| June '07 | 56 | Whk., N. | 4.77 | 2.55 | 4.23 7-drill {| June '07 | 58 | " S. | 4.82 | 2.26 | 3.88 | | | | | | 8-drill {| May '07 | 60 | Hack., N. | 4.67 | 2.44 | 5.00 {| May '07 | 60 | " S. | 4.54 | 2.57 | 4.80 ----------------+-----------+----+-----------+------+------+------
TABLE 2.
Hrs. Hours. Min. Minutes.
----------------+----------+---------------+---------------- Date. | Place. | Total | Number of feet | | working time. | drilled. ----------------+----------+---------------+---------------- | | Hrs. Min. | Jan. 14th, 1907 | Whk. N. | 8 0 | 15 " 15th, 1907 | " N. | 7 32 | 12 | " N. | 7 22 | 14 " 12th, 1907 | " S. | 8 0 | 20 | " S. | 8 0 | 11 | " S. | 8 0 | 10 " 11th, 1907 | Hack. N. | 8 0 | 13 " 17th, 1907 | " N. | 7 10 | 10 | " N. | 7 5 | 11 | " N. | 7 10 | 10 " 16th, 1907 | " S. | 4 20 | 10 | " S. | 6 9 | 10 | " S. | 7 ... | 8 ----------------+----------+---------------+--------------- Totals. | | 93 48 | 154 ----------------+----------+---------------+--------------- Average: 36.6 min. per