CONCRETE CYLINDER PILES AT OREGON INLET, NORTH CAROLINA

摘要

The North Carolina Department of Transportation (NCDOT) has been testing and designing bridges with concrete cylinder piles since the early 1980s. However, their widespread use in production has been limited. In 1996, a 42.7 m (140 feet) long, 1.68 m (66 inches) diameter concrete cylinder test pile was driven and load tested at Oregon Inlet, North Carolina for the design of a new replacement bridge. Oregon Inlet is a 762 meter (2,500 feet) wide marine channel in a very dynamic scour and sediment transport environment lying just off the North Carolina mainland, separating Bodie and Hatteras Islands. Scour and vessel impact loads governed the new bridge foundation design. The installation of the test pile helped determine the drivability characteristics in this type of environment. Two – 10.2 cm (4 inches) diameter, 33.6 meters (110 foot) long jets were used along side of the pile. The pile was jetted and driven throughout the entire installation process. Due to the pile size and soil conditions, jetting was the primary installation method. An HPSI 3505 single acting hydraulic hammer facilitated the installation. At the end of initial drive, the pile was struck 323 times, and the pile did not move. Following the installation of the cylinder pile, it was axially load tested to 220% of the pile design load and laterally load tested until structural failure from bending.