N.J. Admin. Code § 19:6-2.55
Current through Register Vol. 56, No. 24, December 18, 2024
Section 19:6-2.55 - Caisson piles(a) Caisson piles shall denote concrete filled pipe piles that are socketed into bedrocks of classes 1-65, 2-65 or 3-65 and constructed with steel cores.(b) Pipe or shell and concrete shall conform to the requirements for concrete filled pipe piles, except that the minimum compressive strength of the concrete at the age of 28 days shall be 3,500 psi. Steel cores shall conform to the requirements for steel H piles. Reinforcing steel cages shall be covered with at least 1-1/2 inches of concrete.(c) The design of the rock socket shall be predicated on the sum of the allowable bearing pressures on the bottom of the socket plus bond along the sides of the socket. The allowable bearing pressure on the surface of the rock at the bottom of the socket may be increased for embedment in accordance with note 8 or table 613.7, provided that the strength of the concrete fill the socket, computed as 0.45f'c, is of comparable magnitude. The allowable bond stress between the concrete and the sides of the socket shall be taken as 200 psi.(d) Spacing and minimum dimensions are: 1. Minimum diameter of a caisson shall be 18 inches with a minimum shell thickness of 3/8 inch. Minimum depth of the rock socket shall be equal to the diameter of the pipe.2. The center-to-center spacing of caissons shall be at least 2-1/2 times the outside diameter of the shell.(e) Installation rules are: 1. The steel shell shall be installed through overburden, the material within the shell shall be removed, and the shell seated in the rock sufficiently to stop the inflow of soil. Where required to extend the shells, splices are to be welded. A suitable steel driving shoe shall be welded to the bottom of each caisson.2. A socket shall then be drilled in the rock to the required depth and shall be approximately of the same diameter as the inside diameter of the shell. Before placement of concrete, the socket and shell shall be thoroughly cleaned and the rock inspected to verify that the rock is of the class on which the design has been predicated, or of a better class. In case visual inspection cannot be made because of inability to unwater the caissons by standard pumping methods, drilling logs and screenings from the rock drilling operation may be utilized to determine the class of rock in the socket.3. Where more than one section of steel core is required, the mating ends of the sections shall be spliced so as to safely withstand the handling stresses to which they may be subjected. The ends shall be milled or field ground to insure contact. The steel core shall be centrally installed in the caisson before grouting and concreting, shall not be more than one inch above the rock at the bottom of the socket, and shall be full length of the caisson or extend a sufficient distance up into the shaft to transmit the load in the steel core into the concrete of the caisson. A minimum-weight 36 pound stub core beam shall be installed in the socket for caissons not requiring steel cores in order to lock the caissons into the rock. In these cases, the length of the steel cores shall be twice the socket depth.4. Concrete and grout shall be placed so that it completely fills the shell, the socket, and the space between the steel core and shell, and in a manner that will preclude separation of the ingredients.5. If the leakage of water into the caisson is minor, the caisson shall be pumped out and one cubic yard of grout shall be placed in the caissons and then the balance of the concrete installed. If the leakage of water makes it inadvisable to attempt to place concrete in the dry, the shell shall be filled to its top with clean water, and the concrete placed by the tremie method to the top of the caisson in one continuous operation or by using a seal of grout of the same strength as the specified concrete. The grout seal, if used, shall be deposited by means of a grout pipe to an elevation of at least three feet above the cutting edge, and after a sufficient time has elapsed to allow the grout to set, the caisson shall be pumped dry and and the remaining space filled with concrete. N.J. Admin. Code § 19:6-2.55