Laterally Loaded Piles in an Embankment of Dry Sand-Paper

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The article describes the design and construction of foundations for an 8.3 m-high sound barrier along Amsterdam’s Nieuwe Leeuwarderweg. Because the barrier also serves as a traffic safety barrier, its foundations must resist substantial lateral and axial loads, including potential vehicle impacts and negative skin friction from embankment settlement. Open-ended steel tubular piles, up to 914 mm in diameter and 20 m long, were selected and installed by high-frequency vibro driving to limit construction noise.<br /><br />An extensive ground investigation included CPTs and Cone Pressure Meter (CPM) tests. CPM-derived soil stiffness values differed considerably from conventional estimates based on cone resistance. Using the more representative CPM results allowed the designers to optimize pile dimensions and reduce steel requirements.<br /><br />Piles were located close to steep embankment slopes, where a nearby water pond further reduced soil resistance. Plaxis finite-element analyses showed that slope conditions could increase pile-head deflection substantially; both modelling approaches indicated about a 70% reduction in passive soil resistance. The remaining design calculations therefore applied a corresponding reduction to soil parameters.<br /><br />Driving through dense, dry embankment sand proved difficult. Contrary to usual expectations for large-diameter open-ended piles, soil plugging occurred at some locations, sharply increasing driving resistance and causing refusal or pile-head damage. Measures such as larger hammers and lubrication were insufficient. Augering out the plug restored acceptable resistance and enabled installation to the required depth.<br /><br />The study concludes that tubular piles can provide an economical foundation for large lateral loads, but recommends CPM testing for reliable stiffness estimates, finite-element analysis near steep slopes, and explicit consideration of plugging in drivability assessments—even for large piles.

Keywords

sound barrier

foundation design

steel tubular piles

high-frequency vibro driving

negative skin friction

Cone Pressure Meter

plaxis finite-element analysis

embankment slope

soil plugging

drivability assessment