The forms for the piles were set on end on small pile platforms located close to the positions to be occupied by the piles and were braced to the old pier. The forms were of wood and the bulb point, the shaft and the knee braces were molded in one piece. Round iron rods were used for reinforcement. The concrete was composed of 1 part Vulcanite Portland cement, 2 parts of fine and coarse sand mixed and 4 parts of gravel 1 in. and under in size. The mixture was made wet and was puddled into the forms with bamboo fishing rods, which proved very efficient in working the mixture around the reinforcing rods and in getting a good mortar surface. The concrete was placed in small quantities; it was mostly all hand mixed. The forms were removed in from 5 to 7 days, depending on the weather.
The piles were planned to be sunk by water jet and to this end had molded in them a 2-in. jet pipe as shown. They were sunk to depths of from 8 ft. to 14 ft. into the beach sand. Water from the city water mains at a pressure of 65 lbs. per sq. in. was used for jetting; this water was furnished under special ordinance at a price of $1 per pile, and a record of the amount used per pile was not kept. The piles were swung from the molding platforms and set by derricks and block and fall. The progress of jetting varied greatly owing to obstructions in places in the shape of logs, old iron pipes, etc. In some cases several days were required to get rid of a single pipe. In clear sand, with no obstruction, a 12-in. pile could be jetted down at the rate of about 8 ft. per hour, working 1 foreman and 6 men. The following is the itemized actual cost of molding and sinking a 26-ft. pile with bulb point and knee braces complete:
| Forms— | Cost per pile. | |
| Lumber, 340 ft. B. M. @ $30 | $10.20 | ... |
| Labor (carpenters @ $2.50 per day) | 12.00 | ... |
| Oil, nails, oakum, bolts, clamps, etc. | 1.20 | ... |
| ——— | ||
| $23.40 | $ 3.90 | |
| Times used | 6 | |
| Reinforcement— | ||
| 275 lbs. of plain ¾-in. steel rods @ 2 cts. per lb. | $ 5.50 | ... |
| Preparing and setting, 4/10 ct. per lb. | 1.10 | 6.60 |
| Jet Pipe— | ||
| 26½ ft. of 2-in. pipe @ 10 cts. per ft. in place. | 2.65 | ... |
| Setting Forms— | ||
| 6 men @ $2.50 per day = $15, set 4 piles | 3.75 | ... |
| Material— | ||
| 90/100 Cu. yds. gravel @ $1.50 per yd. | 1.35 | ... |
| 45/100 cu. yds. sand @ $1.50 per yd. | .67 | ... |
| 1.50 bbls. cement @ $1.60 | 2.40 | 4.42 |
| Labor— | ||
| Concrete and labor foreman | 3.00 | ... |
| 6 laborers, mixing and placing by hand, $1.75 each | 10.50 | ... |
| ——— | ||
| $13.50 | 3.38 | |
| Average number of piles concreted per day | 4 | |
| Removing Forms— | ||
| 4 men @ $2.50 remove and clean in half day 4 columns | 1.25 | ... |
| 1 man @ $2.25 plastering column with cement grout (4 per day) | .56 | ... |
| Jetting 10 ft. into Sand— | ||
| Foreman | $ 3.00 | ... |
| 4 men, $2.25 each, handling hose and traveler | 9.00 | ... |
| ——— | ||
| $12.00 | 3.00 | |
| Average number of piles jetted per day | 4 | ... |
| City water pressure used for jetting @ $1 per pile | ... | 1.00 |
| Superintendence @ $5.00 per day | ... | 1.25 |
| Caring for trestle, traveler, material, etc. | ... | 4.84 |
| ——— | ||
| Total cost per pile | $36.60 |
The pile being 26 ft. long, the cost in place was $1.41 per foot. Subtracting the cost of sinking amounting to $7.09 per pile, we have the cost of a 26-ft. pile molded and ready to sink coming to about $1.10 per foot. It should be noted that this is the cost for a pile of rather complicated construction; a plain cylindrical pile should be less expensive.
Method of Molding and Jetting Square Piles for a Building Foundation.—The foundation covered about an acre. The soil was a deposit of semi-fluid mud and quicksand overlying a very irregular rock bottom and encircled by a ledge of rock. The maximum depth of the mud pocket was 40 ft., and interspersed were floating masses of hard pan. Soundings were made at the locations of all piles; a ½-in. gas pipe was coupled to a hose fed by city pressure and jetted down to rock, the depth was measured, the sounding was numbered and the pile was molded to length and numbered like the sounding. In all 414 piles were required, ranging in length from 1½ to 40 ft.; all piles up to 6 ft. were built in place in wooden forms. The piles were 13 ins. square and were of 1-2½-4 concrete reinforced with welded wire fabric. A tin speaking tube was molded into each pile at the center. This tube was stopped about 10 ins. from the head and by means of an elbow and threaded nipple projected through the side of the pile to allow of attaching a pressure hose. The piles were handled to the pile driver, the hose attached and water supplied at 100 lbs. pressure by a pump. Churning the pile up and down aided the driving. A hammer was used to force the piles through the hard pan layers. A wooden follower was used to protect the pile head. A 2,800-lb. hammer falling 20 ft. did not injure the piles. One pile was given 300 blows with a 2,800-lb. hammer falling 12 ft., and when pulled was unbroken. It was found that 30 ft. piles and under could be picked up safely by one end; longer piles cracked at the center when so handled. These long piles were successfully handled by a long chain, one end being wrapped around the pile at the center and the other end similarly wrapped near the head; the hook of the hoisting fall was hooked into the loop of the chain and as the pile was hoisted the hook slipped along the chain toward the top gradually up ending the pile. The piles weighed 175 lbs. per lin. ft. It was attempted to mold the piles directly on the ground by leveling it off and covering it with tar paper, but the ground settled and the method proved impracticable.
Method of Molding and Jetting Piles for Building Foundations.—In a number of foundations Mr. Frank B. Gilbreth has used a polygonal pile, either octagonal or hexagonal, with the sides corrugated or fluted as indicated in Fig. 61. In longitudinal section these piles have a uniform taper from butt to point and have flat points. Each pile is cored in the center, the core being 4 ins. in diameter at the top and 2 ins. at the bottom end. On each of the octagon or hexagon sides the pile has a half-round flute usually from 2½ to 3 ins. in diameter. The principal object of these flutes or "corrugations" is to give passage for the escape to the surface of the water forced through the center core hole in driving the pile. They are also for the purpose of increasing the perimeter of the pile and thereby gaining greater surface for skin friction.
The piles are reinforced longitudinally and transversely. On this particular job the reinforcement was formed with Clinton Electrically Welded Fabric, the meshes being 3 ins.×12 ins.; the longer dimension being lengthwise with the pile and of No. 3 wire; the horizontal or transverse reinforcement being of No. 10 wire. The meshes being electrically welded together, the reinforcement was got out from a wide sheet taking the form of a cone. No part of the reinforcement was closer than 1 in. from the outside of the concrete. In general only sufficient sectional area of material is put in the reinforcement to take the tensile stresses caused by the bending action when handling the pile preparatory to driving; more reinforcement than this only being necessary when the piles are used for wharves, piers or other marine structures, where a considerable length of pile is not supported sidewise or when they are subjected to bending stresses.
Fig. 61.—Cross-Section of Corrugated Reinforced Concrete Pile.