Evaluation of measured and interpreted failure loads of bored piles in alluvial soil deposits

Abstract

This paper presents an evaluation of the ultimate load carrying capacity of bored piles measured directly and obtained from selected methods of load test data interpretation based on different failure criteria. Large scale bored piles were installed in alluvial soil deposits and statically loaded to failure. The measured failure loads varied from 195 to 520kN and pile displacements of 1.3 to 2.7%D were required to mobilize such loads for the considered test conditions. The pile shaft friction component contributed over 83% of the total measured ultimate capacity and was fully mobilized at displacements of 0.2 to 0.8%D. A rigorous analysis was carried out to compare the measured and interpreted pile failure loads and evaluate the performance of six published load test interpretation methods. Based on the evaluation results, the L1-L2 and the Fuller and Hoy's interpretation methods indicated the best overall performance in estimating the failure loads. The De Beer and Van der Veen methods revealed similar and fairly good evaluation ratings whereas the Davisson interpretation method showed a relatively poor performance. The Chin's method exhibited a gross overestimation of measured ultimate capacities and among all yielded the poorest overall performance.