Expansion at a prominent local private college-prep academy included construction of a deep foundation system. Our crews installed micro-piles to an average depth of 120 feet. A down-the-hole (DTH) hammer simultaneously drilled and installed casing to the required final depths as monitored by the owner’s geotechnical/field engineer.
Unforeseen subsurface conditions resulted in uncontrollable grout losses during the installation of the ACIP piles at this site. Micro-piles employing casing were installed simultaneously during drilling to solve this problem and to allow the building contractor to complete the work with minimal disruption and delay.
A high (shallow) water table and the proximity of the site to the Ala Wai Canal presented a multitude of problems. Drilling techniques were modified to reduce the quantities of water generated. Admixtures assisted in minimizing grout travel in the soft subgrade materials, and in areas where the design team suspected subsurface water flows.
To minimize the potential for excessive grout consumption associated with poor subsurface conditions in the upper length of the piles, 65 feet of casing was left in place in the unbonded length with an uncased/bonded length of approximately 55 feet.
Project highlights include:
5½”Ø x .361 casing
1d” Grade 150 Epoxy-coated threaded reinforcing bars