LATERAL PERFORMANCE OF HOLLOW BAR MICROPILE IN COHESIONLESS SOIL-Paper

Paper

Pdf Summary

The study evaluates the lateral behavior of a full-scale hollow bar micropile installed in medium-dense to dense sand. The tested pile was 6 m long, with 5.75 m embedded, and used a 51 mm hollow bar with a 115 mm drill bit. Field testing applied monotonic lateral loads in 3 kN increments to a free pile head; horizontal displacement was measured throughout.<br /><br />The load–displacement response was approximately linear up to about 3.5 mm of movement, then became nonlinear. The pile showed no apparent failure by the test limit of 25 mm displacement. Five accepted criteria produced interpreted lateral capacities ranging from 7.3 to 18.4 kN, depending on the displacement threshold. The authors recommend using the load at 25 mm displacement, with a factor of safety of 2, for design.<br /><br />The pile was analyzed using LPILE, which models soil–pile interaction with nonlinear p–y curves. Its predictions agreed well with field measurements, though the model was stiffer at the earliest load increments and slightly less stiff at higher loads. The analysis indicated long, flexible-pile behavior, with soil properties in roughly the upper eight pile diameters strongly influencing lateral response. A plastic hinge was predicted at about five pile diameters below the ground surface, and the maximum bending moment was approximately 8.9 kN·m.<br /><br />Overall, the results suggest that LPILE can reasonably reproduce the measured lateral response of hollow bar micropiles in cohesionless soil. The study also emphasizes that near-surface soil conditions and pile-head restraint are important considerations in assessing lateral performance.

Keywords

micropile

hollow bar pile

lateral load test

sand

load-displacement response

LPILE

p-y curves

bending moment

pile-head restraint

cohesionless soil