Axial resistance of long rock-socketed bored piles in stratified soils

This paper presents the results of static compression load tests performed on long rock-socked bored piles installed in stratified soils. Three bored piles with 34 m in embedded length were instrumented in order to separate the shaft and base resistance, and to allow the determination of the distribution of shaft resistance along the pile shaft. Conventional methods of estimating shaft resistance were assessed. It was found that more than 78% of the shaft resistance was provided by shaft friction at the end of tests. The base resistance has not been fully mobilized in the test. The recommendations of Chinese technical code (JG94-2008) to estimate the shaft resistance were more conservative for long rock-socketed bored piles. Empirical correlations to estimate the shaft resistance are limited due to different geological conditions. The methods which incorporated parameters directly interpreted from standard penetration test (SPT) results provided the most consistent estimates.