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Bulletin 86 



Avenue, built in 1914, and the other the outfall sewer, built in 1917. 

 The same forms were used on both jobs. They are four feet 

 long and the pipe is 30 inches inside diameter with a shell 3^ inches 

 thick. The pipe for the water-supply line was made at a yard, in 

 the center of which was a high derrick. The boom was long and 

 reached over a wide area. Each pipe was moved from the pouring 

 floor out into the yard just before removing the forms and the der- 

 rick was used again later to load the pipe for hauling to place along 

 the trench. The concrete mixture was 1 of cement, 2 of sand, and 

 4 of broken stone or screened gravel. The reinforcement was of 

 round iron wound spirally and was designed to withstand an inter- 

 nal pressure, varying from zero at the upper end to 30 pounds per 

 square inch at the lower end of the line, with 15,000 pounds per 

 square inch allowable working stress in the steel. 



For the outfall sewer the pipe was made along the trench and 

 the forms were moved along as the work progressed. This obviated 

 the necessity of hauling the pipe long distances, but required much 

 hauling while making and curing the pipe. The mixture was the 

 same as for the water-supply line, but the reinforcement was uni- 

 form the whole length of the line and consisted of 3^ inch round 

 iron rings spaced 6 inches apart, and 4 rods of the same size running 



longitudinally through each 

 joint from the end of the 

 tongue to the end of the 

 groove. The maximum dif- 

 ference in elevation in the 

 sewer line is 7?) feet. 



The only criticism of the 

 pipe just described is that 

 the longitudinal reinforce- 

 ment does not extend con- 

 tinuously across the joints. 

 This continuity can be ob- 

 tained in various ways, and 

 some ingenious joints have 

 been patented, notably the 

 Johnson and the Meri- 

 wether, the former of which is shown in Fig. 15. The Johnson pipe 

 uses special bar reinforcement, and the Meriwether uses "Triangle 

 Mesh." Ordinarily longitudinal reinforcement is not needed. It 

 is needed, however, if the bed of the trench is of uneven bearing 

 power and settlement is liable to occur. An inverted siphon laid 



Fig. 15. — The Johnson reinforced pipe joint. 

 (From Bulletin 55.) 



