Construction Sequence for Settlement Control at Bridge End Bents and Reducing Drag Load on HP Piles-Video

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The presentation describes a design-build bridge project in Rocky Mount, North Carolina, where soft soils beneath new embankments could settle and create pile drag loads. Piedmont residual silts and clays often consolidate faster than coastal-plain soft clays. Initial calculations suggested roughly 100 kips of drag load and pile driving resistance above 600 kips.<br /><br />To reduce the load, the contractor built the new embankment before completing the area around the pile cap, leaving a gap to be backfilled later. Piles were driven first and restruck after the embankment had time to settle. This sequence reduced the estimated drag load to about 10–15 kips and required driving resistance to roughly 400–440 kips. Settlement measurements showed about 0.5–0.6 inches overall, with little expected at the pile locations.<br /><br />In discussion, a geotechnical engineer cautioned that hollow-stem auger drilling below the water table can disturb soils and produce misleadingly low blow counts; regularly filling the auger with water can help prevent this.

Keywords

bridge design-build

pile drag load

soft soil settlement

embankment construction sequence

geotechnical engineering