A Study of Laterally Loaded Piles after Failure

Lateral large-scale testing of two pile specimens with a diameter of 0.46 m and a total length of 4.57 m was performed up to complete structural failure. The piles were embedded in 1.83 m of loose backfill sand with a relative density of 20%. At the tip, the piles were embedded in 1.22 m of simulated rock. Pile yield occurred at a lateral pile head displacement of 6.35 cm. The piles reached an ultimate capacity (Pult) near 72 kN at a corresponding pile head displacement of 20 cm. Post-test soil excavation around the piles was used to document pile damage and crack propagation. The originally predicted shear failure did not occur; rather, a flexure-triggered failure through the formation of a plastic hinge above the rock-socket was observed. Upon failure investigation, soil material was placed back into the excavation, and additional soil was placed with the same technique to raise the fill height above the rock socket from 1.83 to 3.05 m. The unique test setup allowed for re-testing of the damaged pile specimen, which is rarely possible in practice. Important understanding can be drawn from the test repetition: (1) magnitude of residual capacity of the damaged pile, (2) assessment of soil resistance independent of the pile as the pile was previously loaded to failure, and (3) evaluation of potential retrofit or repair strategies upon partial or full loss of structural pile integrity. Retesting with 64% more soil compared to the original soil thickness provided an additional 80% capacity compared to Pult of the damaged specimen.