Transactions of the American Society of Civil Engineers, Vol. LXVIII, Sept. 1910 / The New York Tunnel Extension of the Pennsylvania Railroad. / The North River Tunnels. Paper No. 1155

by Bertram Henry Majendie Hewett; W. L. Brown

[C] ]Figures taken from typical cross-sections.

[D] This gives the actual amount of drilling done and powder used per cubic yard for the whole period of 5 months of observation, but as this length included 280 ft. of heading and only 220 ft. of bench, the average figures (for powder especially) are too low.

[Table 6] gives the rate and cost of drilling, and the cost of powder. It will be seen that the average rate of drilling was 2.71 ft. per hour per drill or 27.1 ft. per drill per shift.

[Table 7] shows the result of observation as to the time taken in various subdivisions of the drilling operations. These observations were not carried on for a long enough period to give correct results, but the percentages of time spent on each division of the operation are believed to be about right. The headings of this table are self-explanatory. The necessary delays include all time spent in changing bits, making air-line connections, etc. The unnecessary delays are stoppages caused by lack of supplies or insufficient air pressure.

By [Table 6] it will be noticed that the cost of labor for drilling and sharpening steels was about $0.29 per lin. ft. of hole drilled. The total cost, including repairs, supply of air, etc., came to about $0.38, as will be seen from [Table 8].

Timbering.—On the New York side nearly the whole length of the excavation needed timbering, to a greater or less extent, and for the most part required timbering of quite a heavy type.

TABLE 6.—Rock Tunnel Excavation under 32d Street, East of Cut-and-Cover Section. Drilling and Blasting.—Detailed Cost of Labor in Drilling, also Quantity and Cost of Powder Used.

Drilling and Blasting.																	Powder Used.
Type.	Date.	Total feet drilled.			No. of drill shifts (10-hour.)			Feet drilled per man per hour.			Quantity of excavation, in cubic yards.		Cost of labor only. Drilling and sharpening.				Total Quantity.	Cost per cubic Yard at 11 cents per pound.
													Total.	Per linear feet.	Per cubic yard
															Actual.	Paid for.		Actual.	Paid for
	1907	Heading	Bench	Total	Heading	Bench	Total	Heading	Bench	Total	Actual.[E]	Paid for[F]					Pounds.
													$	$	$	$		$	$
Ke.	May	2,971	5,578	8,549	98	204	302	3.031	2.734	2.831	1,736	1,664	2,331	0.27	1.34	1.40	1,595	0.10	0.10
	June	2,093	6,194	8,287	85	223	308	2.462	2.777	2.691	809	698	2,440	0.29	3.01	3.49	1,960	0.27	0.31
	July		7,627	7,627		268	268		2.845	2.845	1,022	960	2,031	0.26	1.98	2.11	966	0.10	0.11
	Aug.		2,552	2,552		95	95		2.688	2.688	743	716	640	0.25	0.86	0.89	430	0.06	0.07
	Sept.		2,133	2,133		79	79		2.700	2.700	238	238	533	0.25	2.24	2.24	280	0.13	0.13
	Total	5,064	24,084	29,148	183	869	1,052	2.767	2.770	2.770	4,548	4,276	7,975	0.27	1.75	1.87	5,231	0.13	0.13
Ki.	May	6,976		6,976	216		216	3.229		3.229	614	527	1,604	0.23	2.61	3.04	1,230	0.22	0.26
	June	4,089		4,089	135		135	3.029		3.029	357	259	1,234	0.30	3.45	4.76	1,036	0.32	0.44
	July		3,733	3,733		140	140		2.666	2.666	530	404	1,084	0.29	2.04	2.68	550	0.11	0.15
	Aug.		6,715	6,715		249	249		2.769	2.769	925	890	1,901	0.28	2.05	2.13	905	0.10	0.11
	Estim		14,742	14,742		46	546		2.700	2.700	3,254	2,908	4,570	0.31	1.40	1.57	2,470	0.08	0.09
	Total	11,065	25,190	36,255	351	935	1,286	3.152	2.694	2.819	5,680	4,988	10,393	0.29	1.83	2.08	6,191	0.12	0.14
Ko.	May		1,617	1,617		55	55		2.921	2.921	250	188	471	0.29	1.88	2.50	376	0.17	0.22
	June		2,948	2,948		107	107		2.755	2.755	496	347	883	0.29	1.78	2.54	357	0.08	0.11
	July		3,734	3,734		131	131		2.850	2.850	626	606	1,003	0.27	1.60	1.65	609	0.11	0.11
	Aug.		8,260	8,260		290	290		2.848	2.848		709	2,161	0.26	3.00	3.04	918	0.14	0.14
	Estim		4,787	4,787		285	285		1.180	1.680	605	535	2,397	0.50	3.96	4.48	762	0.14	0.16
	Total		21,346	21,346		868	868		2.460	2.460	2,695	2,385	6,915	0.32	2.57	2.90	3,022	0.12	0.14
Grand Total		16,129	70,620	86,749	534	2,672	3,206	3.020	2.710	2.710	12,923	11,649	25,283	0.29	1.96	2.17	14,444	0.12	0.14

The work done during the 5 months when these analyzed cost figures were kept includes 280 ft. of bench and 220 ft. of heading. This excess of bench over heading causes the general average amounts per cubic yard to be too low.

[E]Actual amount of excavation.