no 



Bulletin 86 



4-inch concrete jacket containing substantial horizontal reinforce- 

 ment. After this experience the design of gate pits was changed 

 and they were all built with the lowest section heavily reinforced. 

 None of the reinforced pits gave any trouble. 



In the early summer of 1918 a great deal of trouble was had with 

 a 20-inch pipe line when the water was put in the line. The failures 

 were bv long longitudinal cracks running along the top and the 



iVaST ^IDB ^OUTH 3lDB BAST ^IDB NOQ-TH ^IDB 



Fig. 20. — A cracked gate pit at Continental, caused by expansion of pipe line. 



bottom of the line. In the first break twenty-two lengths of pipe 

 were cracked both top and bottom. In this case the break occurred 

 at a bend in the line about midway between two gate pits, both of 

 which had been reinforced. The bend was the point of greatest 

 weakness, and a heavy longitudinal shear must have been developed 

 in the pipe. The line was under only three pounds internal pressure 

 and the fractured pipe was found to be dense and hard. Fig. 21 is 

 a picture of the second break. Each time, as soon as a break was 

 repaired and the water was turned into the line another similar 

 break occurred. The breaks were confined wholly to the 20-inch 

 pipe, though one pipe line telescoped where a 14-inch pipe joined a 

 16-inch. The 20-inch pipe was made in the summer of 1917 and 

 was stacked in the open air where it became bone-dry. The pipe 

 was laid early in 1918, but no water was turned into it until April. 

 When it seemed apparent that the 20-inch pipe were failing from 

 longitudinal compression, the line was broken open at intervals and 

 expansion joints were put in. In some cases where the line was 

 not under pressure the expansion joint was made by leaving about 

 an inch between two pipe and wrapping a band of tar roofing paper 

 around the line, fastening it with wire. Where the line was under 

 some pressure the expansion joint was made with asphalt. A thim- 

 ble of galvanized iron six inches long was first placed on the inside 

 of the joint. The edges of the thimble were sealed with wet adobe 



