Slope Stabilization in the Potomac Group Formation with Continuous Flight Auger Piles-Video

Video Transcription

Video Summary

A Washington, D.C., project stabilized MSE walls on a steep slope using 24-inch auger-cast piles, 55–95 feet long, in stiff Potomac clays with very low residual strength. The piles provided the shear resistance needed to achieve a factor of safety of 1.5. Compared with a drilled-shaft alternative, the approach saved more than $1 million.<br /><br />Construction presented unexpected challenges: augers became stuck, grout communicated between piles, high pumping pressures sometimes lifted the auger, and reinforcement cages hung up near the pile tips. Grout-volume estimates from thermal integrity profiling were misleading because they relied on reported grout volumes rather than directly measuring pile diameter.<br /><br />The team adapted by introducing air during drilling, reducing grout pressure and pump power, modifying the grout mix, and lifting the auger slightly before pumping. These changes improved cage installation and produced piles close to the auger’s nominal diameter. About 2% of piles were replaced. The project highlighted the value of close field coordination and application-specific quality-control criteria.

Keywords

MSE walls

auger-cast piles

Washington DC

stiff Potomac clays

slope stabilization

grout quality control