Anchored Hollow Bar Tangent Pile System For Underpinning-Video

Video Transcription

Video Summary

A hospital addition required underpinning existing foundations 5–15 feet below grade, but clean, cohesionless sands made the specified pit-underpinning method unsafe and difficult to execute. The team evaluated permeation grouting, but field tests showed it would require multiple rounds and was impractical within the project’s schedule and budget.<br /><br />Instead, they installed micropiles through the existing footing, followed by a temporary soil-nail wall with shotcrete facing. The piles supported the building and helped contain the soil; soil nails and shotcrete stabilized the excavation. The system was installed in stages, with the pile spacing adjusted for a second wall after the first performed well.<br /><br />Despite limited time for baseline monitoring, measured movements were generally modest. The approach proved faster and lower-risk than pit underpinning, helping recover some schedule. The presenter emphasized that underpinning requires experienced designers and contractors, careful sequencing, and appropriate monitoring.

Keywords

hospital underpinning

micropiles

soil-nail wall

shotcrete facing

foundation stabilization

permeation grouting