Popular Science Monthly 



Vol. 88 

 No. 5 



239 Fourth Ave., New York 



May, 1916 



$1.50 

 Annually 



Workmen Shot From Tunnel 

 Through the Bed of a River 



Bv Eustace L. Adams 



BROOKLYN BRIDGE was jammed 

 with mid-afternoon traffic. On the 

 East River, far underneath the 

 lofty structure, tugs and barges were 

 busy with their endless tasks. Suddenly 

 passengers on the bridge and crews of 

 boats heard a muffled roar, and a geyser 

 shot from the rixer twenty feet into the 

 air. Dark forms mingled with the water, 

 and a moment later, when the rush of the 

 geyser had died down, three men were 

 seen floating on the surface of the river. 



One of these men quickly disappeared 

 from sight. His dead body was later 

 recovered. The other two swam for shore 

 and were rescued. One of them died 

 before he could be taken to the hospital. 

 The other lived. All three men (sand 

 hogs, who had been digging in an 

 atmosphere of compressed air under the 

 river) had been blown from their posts in 

 front of the great steel shield which is 

 boring through the East River bed to the 

 open air. They were shot through 

 twenty-seven feet of river mud, twenty- 

 five feet of water and an additional 

 twenty into the air on top of a geyser of 

 mud and foam. 



The first knowledge that the officials 

 at the Brooklyn end of the new subway 

 tube had of the accident was when a 

 number of terrified workmen rushed into 

 the compressed air caisson, clamoring 

 to be let out. Among these was one 

 man who had been a witness of the acci- 

 dent, and from him a coherent story was 

 obtained. 



The tunnel in which this strange acci- 

 dent occurred had been pushed out under 



the river for about three hundred feet, 

 by what is known as the shield method. 

 When engineers commence their under- 

 ground tunneling, a heav^^ steel shield 

 is built at the end of the shaft where the 

 men are at work. This shield is pushed 

 forward into the mud or dirt for a dis- 

 tance of two feet by a number of hy- 

 draulic rams which are capable of 

 exerting a pressure of five thousand 

 pounds to the square inch. In the shield 

 are a number of doors which allow the 

 workmen, or "sand hogs," to dig away 

 the dirt, stones and mud in front so 

 that the shield may be moved another 

 two feet. • 



The question naturally arises: What 

 keeps the mud and water from coming 

 into the shield and overwhelming the 

 workmen? A short distance behind the 

 shield is a bulkhead wall, containing air 

 locks. The entire space forward from 

 the airlock is kept filled with com- 

 pressed air. This air, when maintained 

 at the proper pressure, balances that 

 of the water and keeps it from flowing 

 into the tunnel. If sufficient pressure is 

 exerted by the air-pumps, the water is 

 dri\cn still farther away, and the work- 

 men ma\' work on dry ground, instead 

 of on mud of a molasses-like consistency. 



As they excavate in front of the shield, 

 the workmen plank up the opening they 

 have made and remove the planks just 

 before the shield is to be pushed forward. 

 The shoring serves merely to keep loose 

 earth and stones from falling upon the 

 men as they work. 



Four men, who were outside the shield, 



643 



