Behavior of Micropiles in Bridge Bent Applications: Fid-Bau Portal

Behavior of Micropiles in Bridge Bent Applications

J. B. Anderson / M. R. Babalola

This project concerned the behavior of micropiles under lateral loads. The North Carolina Department of Transportation was specifically interested in the use of micropiles to support bridge bents. In this configuration micropiles would be subjected to lateral loads. Thus there was a need to evaluate the behavior of micropiles as bridge bent foundations with respect to joints between micropile sections and embedment or plunge in rock. The objectives of this study were to demonstrate the lateral performance of micropiles in single and group configurations, determine the effect of casing plunge on lateral resistance of micropiles, determine the effect of casing joints on the lateral resistance of micropiles, determine the behavior of jointed micropile sections, evaluate the durability of micropile casings and jointed sections, and disseminate the experimental findings to NCDOT. These objectives were investigated using a three pronged approach of numerical modeling, full scale field lateral load tests, and laboratory testing. Sixteen sacrificial micropiles were installed in order to perform six lateral load tests. Rock plunge depths of 1, 2, 5 and 10 feet were investigated. 14 of the 16 piles were two or three sections or more. A cap was cast around four of the piles to create a bent that was load tested against a group of reaction piles. In addition, nine jointed micropile specimens were fabricated and tested in the laboratory under four point flexure. Numerical models were developed to first predict the behavior of the load tests. The results of the field and lab tests were subsequently used to calibrate the model for DOT use. A long term study of the impact of corrosion on micropile sections is submitted for future implementation.