Q.: The piles of an ocean pier have deteriorated to the point where they have to be repaired soon, and some of the reinforcing steel will have to be replaced. The thickness of the repair will vary from about 1 1/2 to 3 inches and we would like a recommendation of a good method of forming and concreting.
A.: Why not use a fabric pile jacket? After all the chipping has been completed and the necessary new steel has been anchored in position, the fabric jacket is hung around it. This is a sleeve tailor-made for the pile and it is provided with a zipper closure. It hangs from a ring in a hem at the top of the sleeve. When the zipper has been closed the bottom is bonded to the pile and the top ring is pulled upward with turnbuckles until it is tight. The repair is made by injecting mortar through two flexible hoses that reach to the bottom of the sleeve on opposite sides of the pile. These hoses are withdrawn as the mortar fills the sleeve.
Two readers of the Problem Clinic item "Repairing Piles in Seawater," October 1981, page 849, have called our attention to methods of repair other than the method we described. The two other methods are described below.
- The first method was successfully used about five years ago on more than 1500 LaGuardia Airport runway piles in Riker's Island Channel. After the deteriorated or damaged pile surfaces have been properly prepared, a crew approaches each pile in a raft or boat at low tide. The raft or boat contains a small mixer and supplies of a two-component epoxy and filler designed for this particular purpose. After a batch is mixed a workman wearing rubber gloves picks up baseball-size globs of the mixture and kneads them onto the piling by hand. It is said that a pile length of about 6 feet can be coated to a thickness of 3/16 inch in about seven minutes after the crew has become experienced. The epoxy to be used for such a surface should be chosen only on the basis of tests simulating the service conditions to be expected.
- The second method makes use of a fiber jacket or fiberglass-reinforced plastic jacket around the pile which serves as a form face during placement of concrete. If a fiberglass-reinforced plastic jacket is used it is left in place to provide strong, rigid protection against erosion, wave action, freezing and thawing, marine-bore attack and chemical attack and to resist impact damage. This kind of jacket also provides a straight, uniform, attractive appearance. Fiberglass-reinforced jackets have been in use for several years and are reported to have gained widespread acceptance by state departments of transportation, port authorities, the United States Navy and the Corps of Engineers. Repairs with them have been accomplished to the mud line in depths up to 60 feet, withstanding pump pressure up to 8600 psf. The success of the fiberglass-reinforced jackets is reported to have been such that the system is now being specified to protect piling in new installations.