A Review of Residual Load Development In Driven Cast-In-Situ Piles-Paper

Paper

Pdf Summary

This case study examines residual load development in four instrumented driven cast-in-situ (DCIS) piles at Avonmouth, England. The piles were 7.5–9.5 m long and installed through soft alluvial clay into dense sand. Strain and temperature were recorded every five minutes from shortly after concrete placement until static load testing, 13–17 days later.<br /><br />Measurements showed that concrete hydration raised temperatures for roughly the first 10 hours, followed by cooling and continued curing. Although initial temperature changes affected the gauges substantially, all gauge levels ultimately recorded net compression, and compressive strains were still increasing when testing began. The authors attribute these strains to a combination of concrete hydration, cooling and curing; soil consolidation as driving-induced excess pore pressure dissipated; and possible groundwater absorption and concrete swelling near the pile toes. The upper gauges may also have reflected structural effects rather than soil movement.<br /><br />The study emphasizes that strain readings at the start of a load test cannot be assumed to be zero. Ignoring residual loads can distort estimates of shaft friction, toe resistance and pile movement. Several interpretation methods produced different residual-load profiles. The Siegel and McGillivray method gave results most consistent with expected negative skin friction from consolidation and with the Unified Design method.<br /><br />The findings demonstrate that DCIS pile strains arise from interacting thermal, concrete and ground processes, and may continue evolving beyond the usual curing period. Reliable interpretation therefore requires continuous monitoring before testing, careful correction for temperature, and test planning that accounts for changes in strain over time.

Keywords

residual load

DCIS piles

pile strain

concrete hydration

temperature effects

negative skin friction

soil consolidation

static load testing

avonmouth

pile interpretation