Design and Construction Recommendations for Driven Piles in Intermediate Geomaterials-Paper

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The paper presents design and construction recommendations for steel driven piles installed in intermediate geomaterials (IGMs), transitional materials with high geological variability that are not adequately addressed by conventional soil-based methods. The recommendations draw on more than 150 pile load tests.<br /><br />The authors propose classification criteria to distinguish soil-based IGMs from soils and rock-based IGMs from hard rock. Fine-grained materials with undrained shear strength above 2.7 ksf are classified as fine-grained IGMs; coarse-grained materials with corrected SPT resistance above 50 blows/ft are classified as coarse-grained IGMs. Shales are further grouped by material type and degree of weathering.<br /><br />New static analysis methods estimate pile shaft resistance and end bearing in fine-grained IGMs, shales, siltstone, sandstone, and claystone. Four wave equation analysis program (WEAP) procedures are also proposed, combining default or improved IGM resistance estimates with either standard or recalibrated dynamic parameters. These methods aim to improve drivability assessment, resistance prediction, and construction control.<br /><br />Load and Resistance Factor Design (LRFD) resistance factors were calibrated using probability-based methods to meet target reliability levels. At a reliability index of 2.33, factors for the proposed static methods vary by material and resistance component; calibrated factors for the four WEAP methods range from 0.83 to 0.85.<br /><br />Finally, the paper recommends using geostatistical tools—including variograms, kriging, and spatial Markov-chain models—to account for subsurface variability and geological uncertainty. These tools can guide the number and spacing of boreholes, improve site characterization, and support more reliable and cost-effective pile design.

Keywords

steel driven piles

intermediate geomaterials

pile load tests

classification criteria

undrained shear strength

SPT resistance

wave equation analysis

LRFD resistance factors

geostatistical tools

kriging