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1902.] 7 MARINE REVIEW. : 15 Algoma Central Railway is also enlarging its dock facilities at Michipico- ten on the north shore of Lake Superior. MORE SUBSTANTIAL FORM OF DOCK CONSTRUCTION. In line with the substantial growth of the ore industry the railway companies and dock companies are also giving thought to the subject of eventually replacing the present form of timber docks with 'concrete structures, built to withstand the rough usage to which docks of the iron ore trade are subjected. The experience of the Illinois Steel Co. (now a part of the Steel Corporation) in this regard is interesting. The accom- panying illustration shows a dock of the concrete kind at the Illinois works, South Chicago. Some information regarding this dock, as well as others of a similar kind at the South Chicago works, is derived from a paper on the subject, prepared by Mr. Victor Windett, engineer of the Illinois Steel Co., who designed these structures. Mr. Windett says: "This dock, known as the south dock of the north slip, replaced a strong timber dock of pine deck on heavy pine caps and sills, carried on three parallel linés of piles, which in each row were spaced 6 ft. apart along the dock. In 1897 and 1898 a fourth line of piles was added to rein- force the dock. At the water line all were tied together by heavy oak ties and wales and 1'%-in. rods (all timbers being 12x12 in. in section). Back of the piling was a line of double 4-in. oak sheeting, behind which, to prevent washing of sand, was 6-in. pine Wakefield sheeting. The dock was tied back by heavy anchor rods every 6 ft. to either a line of piles or before the dock was put in use. In the river silt of New Orleans, this resistance amounted to six tons per foot of length of piles. These piles are in an especially favorable position to absorb the strain on the diagonal bolts of the mooring posts. Had these piles been driven battered towards the dock front, i. e., the upper end of driven pile pointing in shore, the most favorable position would have been to have braced the front piles. This was not possible on account of the closeness of approach to the dock of the rectangular box-like hulls of steel vessels. If placed against the second row of piles, the angle of batter would have been so slight as to have been of little utility. Had this objection been overcome by driving them against the third line of piles, a large portion of them would have been in the comparatively loose slag filling where they would be of doubt- ful value. It is also in favor of the batter piles as driven that they were easily driven from batter leaders temporarily fastened to the leaders of an ordinary floating pile driver. The value of this feature was shown by the ae that these piles were driven for the same price as the ordinary vertical piles. : "Concrete was made of blast furnace slag, as dug by a steam shovel from the slag bank, without further preparation. That portion below the water level was made in the proportions of steel Port- Jand cement one, sand four, slag eight parts. The face was similarly composed in the proportions one, four; four. The backing was made of Utica natural cement one part, sand three, slag five parts. The top was finished with 4 in. of steel Portland, sand, and crushed slag--one, two, two CONCRETE DOCK AT THE ILLINOIS STEEL CO.'S PLANT AT SOUTH CHICAGO. a concrete wall, situated 45 ft. back and running from the ground level about 8 ft. down. The width of this wall was 6 ft. The dock was built in the summer and winter of 1890, but after seven years' use, under the heavy service of the iron ore trade, it was dangerously broken in sections and worn out. When the new dock took its place the front row of piles was closed with Norway pine piles. Piles in the second row were driven 2 ft. centers. Back of this stood a new line, in which piles were spaced 3 ft. centers. All the old dock being cut out of the way, the piles were sawed off at a depth of 3% ft. below Chicago datum. The open spaces between the piles were filled with slag. The front and third rows were tied together by wales and rods every 8 ft. A grillage of 12x12 in. hem- lock timbers, composed of longitudinal caps and cross pieces spaced 21-in. centers, was bolted to the piles. The drift bolts stand 9 in. above the grillage. The concrete superstructure is firmly fastened to this timber work by entirely surrounding the grillage timbers and protruding bolts whose heads are upset to give greater area of contact with the concrete. The stability of the dock depends upon four things. These are: "First--The stiffness of the pile and grillage structure, which is con- siderable. : "Second--The great weight of the dock, exceeding 10 tons per lineal foot and acting in a vertical direction. : "Third--The strong-back anchors, which are 134-in. rods spaced 6 It. apart, running to a line of piles and anchor timber of oak 36 to 38 ft. back of the dock. "The fourth source of strength is a row of batter piles, driven 7 ft. apart, running back under the toe of the old sheeting, in a favorable position for resistance. These piles, passing between grillage timbers, rise into the concrete and are firmly bolted to two side pieces of oak, which in turn are drift-bolted to the grillage. While no direct tests of the strength of this style of anchoring are available. it is known that it 1s extremely difficult to pull a rough pile--entirely below ground and in a stiff clay and with a downward pressure exerted on it--from the superin- cumbent earth above it, especially after it had ample time to come to rest parts respectively--one running into the other in 'saw tooth' form, aver- aging a foot thick. The face had no protection from cold other than the 3-in. pine planking used for the concrete form. During construction, the thermometer fell to 8° and concreting was carried on at temperatures as low as 15°. Expansion joints were provided every 25 ft. At these places the blocks dovetail into each other, to insure permanent uniformity in alignment. "Cast iron mooring posts, weighing 1,500 Ibs. each, are bolted to the grillage by four 2-in. bolts. Additional security is given by diagonal tie- rods running to the anchor piles. Fenders of wales bolted to the concrete and piles are placed in front to take the blow of vessels and distribute them over the mass of the concrete. The fenders form the only part of the dock subject to decay, as all other wood and iron are protected from action of the atmosphere and climatic changes. "Work was begun on this reconstruction Jan. 3, 1899, by tearing out a portion of the old dock. Concreting began Feb. 17. On May 5 1,428 ft. of the entire 1,608 ft. was completed--in ninety-eight working days. This was at the rate of 15 ft. completed per day. In one day of 10 hours 112 piles were driven, and 170 cut off 3% ft. below water, the saw being set each time under an engineer's level. In masonry, 143 cubic yards of concrete were placed in 11 hours, and 130 during the following night turn. "The dock having passed through two summers and parts of three winters shows no sign of the service undergone in the thumping of heavily loaded ore vessels against it, sometimes severe enough to give a strong blow when their headway has not been sufficiently checked before touching the dock fenders. Mooring posts have stood the test of hauling up short vessels coming to a stop. Lines from three vessels have been on a single post at a time. The posts and alignment of the dock remain unchanged. On the land side, within 40 ft. of the dock face, are the rails of the Brown-Hoist.conveyors--two standard gauge tracks on which run 180.000-Ib.. locomotives with 100,000-Ibs. capacity cars, and a 3 ft. gauge ore railway. Immediately behind are ore piles rising to a height of 35 ft. "At the south slip docks the problem in construction was different