1812.3.3 Installation.
BC § 1812.3.3
Where shafts for drilled piles are formed through unstable soils and concrete is placed in an open-drilled hole, a steel liner shall be inserted in the hole prior to placing the concrete. Where the steel liner is withdrawn during concreting, the level of concrete shall be maintained above the bottom of the liner at a sufficient height to offset any hydrostatic or lateral soil pressure. Where drilled displacement piles are used, the auger segments shall be installed into the ground with both a vertical force and a torque such that the soil is displaced laterally within the ground. The void created after installation shall be filled with grout or concrete. Where grout is placed by pumping through a hollow-stem auger, the auger shall be permitted to rotate in a clockwise direction during withdrawal. An initial head of grout shall be established and maintained on the auger flights before withdrawal. The auger shall be withdrawn in a continuous manner in increments of about 12 inches (304.8 mm) each. Grout pumping pressures shall be measured and maintained high enough at all times to offset hydrostatic and lateral earth pressures. Grout volumes shall be measured to ensure that the volume of grout placed in each drilled pile is equal to or greater than the theoretical volume of the hole created by the auger. Where the installation process of any drilled pile is interrupted or a loss of grout pressure occurs, the drilled pile shall be re-drilled to 5 feet (1524 mm) below the elevation of the tip of the auger when the installation was interrupted or grout pressure was lost and reformed. Augered cast-in-place piles shall not be installed within a distance equivalent to the center-to-center spacing equivalent to six times the diameter of a drilled pile filled with concrete or grout less than 12 hours old, unless approved by the engineer. The level at which return of the grout occurs during withdrawal shall be recorded. If the grout level in any completed drilled pile drops during installation of an adjacent drilled pile, the drilled pile shall be replaced. The installation shall be performed under the direct supervision of the engineer. The engineer shall certify to the commissioner that the drilled piles were installed in compliance with the approved construction documents.
