Static Loading Tests And Piled Foundation Design For A Three-Storey Building-Video

Video Transcription

Video Summary

The presentation examined a large high-school project in Perth Amboy, New Jersey, where 1,600, 18-inch auger-cast piles were installed through soft, compressible clay into dense clay. About 16 feet of fill was added, creating potential downdrag. Three full-scale static load tests showed substantial pile capacity, but interpreting the results was complicated by residual loads caused by settling fill. Correcting for residual load revealed that the upper soil’s apparent strength—and thus estimated drag force—had been overstated.<br /><br />The speaker explained that downdrag analysis should focus on pile structural capacity at the neutral plane and settlement, rather than treating drag force as additional pile-head load or applying capacity checks only below that plane. Misinterpretation of building-code language risked adding about 30 feet to pile lengths. Ultimately, only some piles were lengthened by six feet. Better analysis could have saved further costs, highlighting the value of measuring pile strains before load testing.

Keywords

augur-cast piles

downdrag analysis

static load tests

residual loads

neutral plane

pile capacity