Canadian engineer . 3. inside View of Caisson. feet of caulking. The caisson was built on a skidway havinga slope of 1:5. There were five skid timbers, each skidbeing supported by eight piles driven to hard-pan. When 338 THE CANADIAN ENGINEER Volume 22. the caisson was ready to launch, the supporting- timberswere, one at a time, lowered down to the skid timbers whichhad been well greased, and the caisson allowed to slide outin a horizontal position. Before launching, the first sectionsof the man-lock and two material locks were bolted into posi-tion, also all pipe connections through the deck
Canadian engineer . 3. inside View of Caisson. feet of caulking. The caisson was built on a skidway havinga slope of 1:5. There were five skid timbers, each skidbeing supported by eight piles driven to hard-pan. When 338 THE CANADIAN ENGINEER Volume 22. the caisson was ready to launch, the supporting- timberswere, one at a time, lowered down to the skid timbers whichhad been well greased, and the caisson allowed to slide outin a horizontal position. Before launching, the first sectionsof the man-lock and two material locks were bolted into posi-tion, also all pipe connections through the deck and insidefittings placed. These consisted of two 5-inch pipes withflap valves for the air; one 3-inch pipe for water connections,with valves, hose, etc., for three jets; three 4-inch pipes,with valves, hose, etc., for blow-off pipes; one connectionfor high pressure air; two whistle pipes; and electric light-ing weight of concrete were increased as the caisson sank until,at bed rock, 38 feet down, an air pressure of 16 pounds wasused. Boulders and rock were excavated in buckets throughthe material locks; but all clay, gravel and small stoneswere blown out through 4-inch pipes by the pressure withinthe chamber. The upper excavation was a boulder clay, theboulders ranging from small stones up to some the size of abarrel. The lower excavation was a gravelly hard-pan, alsofull of boulders. This had to be picked and spaded beforethe jets would have much effect on it, the blow-pipes weregoverned by 4-inch cast-iron plug-cocks which were opened
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishertoron, bookyear1893
