Fig. 147.—Sketch Showing Detail of Side Wall Forms. New York Subway Tunnels.
As soon as the side wall concrete had set the forms were struck and the traveler was moved ahead and set for another section of wall. The derrick and roof arch travelers were then moved into position between the finished walls, and the arch traveler was jacked up and aligned. Skip cars coming from the mixer were run under the derrick traveler, where the skips were lifted by the derrick and set on the platform cars to be run alongside the work. The arch lagging was placed a piece at a time and filled behind by shoveling direct from the skips. As the crown was approached the lagging was placed in short lengths and filled in over the ends, the concrete being shoveled in two lifts; in Fig. 145 the line C D indicates the position of the shoveling board. The centers were struck by lowering the jack supported traveler down onto the track rails.
COST OF MIXING AND PLACING SUBWAY LINING, LONG ISLAND R. R., BROOKLYN, N. Y.—The subway carrying the two tracks of the Long Island R. R. under Atlantic Ave., in Brooklyn, New York city, has a lining consisting of an invert arch 12 ins. thick at the center, side walls 4½ ft. thick at the base and 3 ft. thick at the top, and a roof of jack arches between steel I-beams 5 ft. apart. The dimensions inside the concrete are 16×20 ft. A 1-8 mixture of cement, sand, gravel and stone was used in the floor and walls and a 1-6 mixture of the same materials in the jack arches. A bag of cement was called 1 cu. ft., so that a barrel was 4 cu. ft. A Hains gravity mixer and a batch mixer were used and careful records were kept of all quantities.
General Data.—During 1903, about 13,880 cu. yds. of the 1-8 concrete were placed, 90 per cent. of which was mixed in the gravity mixer and 10 per cent. in the batch mixer. Of the 1-6 concrete 5,320 cu. yds. were placed, 85 per cent, of which was mixed in the gravity mixer and 15 per cent, in the batch mixer.
Gravity Mixer Work.—During 1903, there were 16,940 cu. yds. of concrete mixed in gravity mixers, requiring 2,860 days' labor mixing and 4,000 days' labor placing. Wages were $1.50 a day and the cost was 26 cts. per cu. yd. for mixing and 33 cts. for placing, making a total of 59 cts. per cu. yd. During the month of August when 2,800 cu. yds. were mixed the cost was as low as 24 cts. for mixing, plus 22 cts. for placing, or a total of 46 cts. per cu. yd. for mixing and placing. The mixer averaged about 113 cu. yds. per day with a gang of 19 men mixing and 26 men placing. The average size of batch was 0.46 cu. yd. In 1904, 20,000 cu. yds. were mixed in 190 days, worked with a gang of 19 men mixing; the gang placing consisted of 25 men. The cost was as follows:
| Item. | Total. | Per cu. yd. |
| 2,950 days labor mixing | $ 4,870 | 24 cts. |
| 4,760 days labor placing | 7,300 | 36 cts. |
| ———— | ———— | |
| Total | $12,170 | 60 cts. |
During the best month of 1904, the labor cost was 16 cts. for mixing and 29 cts. for placing, or a total of 45 cts. per cu. yd.
Batch Mixer Work.—During 1903 the batch mixer mixed 2,390 cu. yds. in 970 labor days mixing and 740 labor days placing at a cost of 59 cts. per cu. yd. for mixing and 55 cts. per cu. yd. for placing, or a total of $1.04 per cu. yd. During the month of June the cost was as low as 40 cts. for mixing and 30 cts. for placing, or 70 cts. per cu. yd. for mixing and placing. The wages paid were $1.50 per day and the average gangs were 11 men mixing and 14 men placing; the average batch mixed was 0.57 cu. yd. and the average output was 35 cu. yds. per day. During 1904, the mixer worked 153 days and averaged 46 cu. yds. per day; the average size of batch was 0.44 cu. yd. The average gangs were 13 men mixing and 11 men placing. The labor cost of 7,000 cu. yds. was as follows: