127 



The lolldwing clfscri])tii)n ol these recent instaUations (if pre-cast concrete pile 

 jackets is (|niiti'<l from Mr. hVank ("i. White, Chief luigineer of the ("alifornia Board of 

 State Harbor Commissioners (writing in 1925)*. 



"Pier 50, the inner unit of which is now under construction, has a width of .^86 feet and when 

 completed it will have a length of 1450 feet. At present it is being built 600 feet long. There are two 

 flush tracks on each side and three depressed tracks and a driveway down the center. The sections 

 under the outside tracks, having a width of 30 feet on each side, are of creosoted pile and timber con- 

 struction. The remainder of the structure is of reinforced concrete on jacketed piles. The conditions 

 arc ideal for this type of construction as the bottom is of such a nature that piles from 70 to 90 feet 

 in length are required while the jackets are only from 26 to 41 feet in length. In previous work by this 

 method the wooden piles were driven tip down as is the usual custom. In Pier 50, however, they are 

 being driven butt down. This gives increased bearing value and permits of using jackets 14 and 16 

 inches in inside diameter instead of 18 to 20 inches as would be necessary' if they were to be placed 

 over the butts of large piles. It also facilitates the introduction of pipes for pumping and grouting. 

 The jackets are circuUir on the inside and octagonal on the outside, the corners being chamfered on 

 a 4-inch be\el. Two sizes of jackets were used depending on the length, the minimum outside dimen- 

 sions being 20 and 22 inches and the mininium thickness ol shell 3 inches. The reinforcement consists 

 of 8' 2-inch square deformed liars spirally wrapped with No. 6 wire on 4-inch pitch. The longitudinal 

 bars protrude 2 feet for bonding into the deck structure. 



"The concrete consists of one part of cement to 4'2 parts of graded aggregate. It is mixetl fairly 

 dry and is thoroughly tamped and spaded after being deposited in the forms. The jackets are kept 



Pig. 47. Pre-cast concrete jackets in place o\er piles. .Alaska Packers' Assn. 



Alameda. 

 {Moulin Photo.) 



covered with wet burlap for two weeks and are not handled for 30 days after being cast. As they are 

 set in position over the piles, the mud is forced out by means of a gasket made of old rubber hose, after 

 which they are sealed by grouting under water. When this grout has set the space between the jacket 

 and pile is pumped out and filled with concrete. The deck is of reinforced concrete construction. 



"The wharves at the Encinal Terminals are being constructed along one side of a dredged slip 

 about 1500 feet in length. Except for modifications in design on account of different local conditions 



*Paper, "Concrete Jacketed Piles,' 

 Association of Port Authorities. 



presented before the 1925 meeting of the Pacific Coast 



