Results of Lateral Load Tests on Micropiles

Results of ten lateral load tests conducted on micropiles are presented. The micropiles were 15.2 m long and reinforced with a centered high-strength threaded bar along the entire length. Bending stiffness and capacity in the upper 9 m of the micropile were increased by including a 244 mm-OD casing with a 13.8 mm thick wall. Lateral load behavior measured during the load tests were compared with behavior predicted using conventional p-y methods originally developed for laterally loaded piles. Predicted and measured displacements usually agreed within 10 percent. Most of the lateral load tests were terminated when lateral displacements exceeded the displacement capacity of the jacks; however, two of the ten micropiles experienced excessive displacement at relatively small lateral load. Excavating beside these two micropiles revealed that excessive rotation occurred at the threaded connection in the casing about 2 meters below the ground surface. The threaded connections in these two micropiles experienced excessive rotation at one-fourth of the first-yield moment as determined from structural tests on an intact casing.