AXIAL CAPACITIES OF DRILLED DISPLACEMENT PILES PREDICTED BY SPT AND CPT BASED METHODS-Video

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The presentation examined axial capacity prediction for drilled displacement piles using a database of more than 100 piles from 45 construction projects, mainly in California, Florida, and Louisiana. Researchers compiled site soil data, CPT/SPT results, pile geometry, and load-test records, then compared analytical capacity estimates with failure loads interpreted from load tests.<br /><br />Because many piles did not reach plunging failure during testing, several interpretation methods were assessed. The Van der Veen method provided the most reliable failure-load estimates. For capacity predictions, the Briaud and NeSmith method performed best in sand-like soils; the Bustamante and Gianeselli method was more accurate in clay-like and mixed soils. SPT methods were less consistent overall, though O’Neill and Reese performed relatively well for sands and mixed soils.<br /><br />The study also found that pile installation can improve soil resistance, particularly in sands, increasing pile capacity beyond estimates based on pre-installation soil tests. The improvement is harder to predict in clays and contractive soils.

Keywords

drilled displacement piles

axial capacity prediction

load test interpretation

Van der Veen method

pile installation effects