Scour Effects on Laterally Loaded Piles in Sand and Potential Remedial Measurements-Paper

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The study examined how scour affects the lateral performance of single piles in sand and whether riprap can restore resistance. Instrumented steel pipe pile models were tested in a large tank filled with dune sand. Scour-hole depths ranged from zero to three pile diameters (D), and lateral loads were applied in increments. Pile-top deflection and strain measurements were used to assess load capacity and bending moments.<br /><br />Scour increased pile deflection under the same load and raised bending moments along the embedded length. At a deflection limit of 5% of the pile diameter, lateral capacity declined as scour depth increased: capacity loss ranged from about 3% at 1D to approximately 20% at 3D. The authors attribute this reduction to the loss of supporting soil and the resulting increase in unsupported pile length.<br /><br />Riprap was tested as a protective measure for the 3D scour case. It substantially improved lateral resistance, increasing the reported ultimate load from 52 N for the scoured pile to 116 N with riprap. The authors suggest that scour should be considered in the design of piles exposed to strong lateral forces, and that riprap may help mitigate its effects.<br /><br />The findings are based on laboratory model tests of a single pile in sand; further study would be needed to establish how the results apply to full-scale foundations and field conditions.

Keywords

scour

lateral resistance

single pile

sand

riprap

pile deflection

bending moments

pile capacity

unsupported length

foundation design