Editorial Note - Vol. 14, No. 2, 2020-Article

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The DFI Journal’s second issue of 2020 presents five papers despite the challenges of the COVID-19 pandemic.<br /><br />The first study examines loss of end-bearing capacity caused by rebound in large-displacement prestressed concrete piles driven in Florida alluvial sands. Silty soils with 20–40% silt are associated with high rebound, which can create tensile stresses and increase the risk of pile failure. The authors offer recommendations for identifying rebound-prone soils using testing and soil classification.<br /><br />The second paper proposes an improved method for estimating the geotechnical resistance of helical piles and anchors. By relating resistance to shaft diameter and final installation torque, the method improves on factors based only on shaft diameter.<br /><br />A third study shows that installation practices—including re-driving, prolonged installation, slow jacking, upper casing, and vibratory hammers—can reduce pile side resistance in plastic soils. The authors propose design modifiers to account for these reductions.<br /><br />The fourth paper uses calibrated Plaxis 3D modeling to study foundations supported by sand compaction columns in loose to medium-dense sands. The model estimates column capacity and failure behavior, and provides coefficients for estimating ultimate bearing capacity.<br /><br />The issue’s student research award paper reports large-scale tests of drilled shafts with simulated rock sockets and varying transverse reinforcement. The specimens failed primarily in flexure, contrary to expectations from p-y analyses. The findings suggest those analyses may overestimate shear demand at soil–rock interfaces, potentially allowing less transverse reinforcement and improving concrete placement.<br /><br />The editorial closes the Journal’s 2020 volume and invites submissions for 2021.

Keywords

COVID-19 pandemic

DFI Journal

prestressed concrete piles

helical piles

geotechnical resistance

pile side resistance

plastic soils

sand compaction columns

drilled shafts

rock sockets