Volume 31, Issue 3 (May 2008)
Toe-Driven Tapered Fiber-Reinforced Polymer Self-Consolidating Concrete Composite Piles: New High-Performance Technology for Deep Foundations
Field experience shows that it has been often difficult to assure the structural integrity and uniformity of the cross-sectional area of cast-in-place concrete piles since cavities and soil pockets tend to form due to the lack of visibility and accessibility during construction. Moreover, corrosion in pre-stressed concrete, reinforced concrete, and steel shell piles has been very costly, exceeding $2 billion of annual repairs in the United States alone. This paper summarizes the findings of a comprehensive research program that was undertaken to develop novel technology that addresses both construction and durability related problems of piles. A new toe-driving technique was developed to install empty fiber-reinforced polymer (FRP) shells into dense soils. A specially developed cost-effective self-consolidating concrete (SCC), a material that flows under gravity and assures the integrity of piles is subsequently cast into the FRP tubes, which provide corrosion-resistant reinforcement. Driving tests were carried out on large-scale model FRP-SCC and steel piles installed in dense dry sand enclosed in a pressure chamber using the new technique along with conventional hammering at the pile head. FRP-sand interface characteristics were evaluated. The pile specimens were instrumented to investigate their dynamic behavior during driving, and their response to static compressive, uplift, and lateral loading. Both cylindrical and tapered FRP-SCC piles were tested. It is shown that the new toe-driving technique is very suitable for installing FRP and other thin-walled piles in dense soils. Results from dynamic pile driving and static load tests indicate that FRP-SCC composite piles are a very competitive and attractive option for deep foundation applications.