A Case Study: Soil Setup for Piles Driven into Eastern Coastal Plain Deposits in Virginia-Paper

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This case study evaluates time-dependent soil setup—the increase in driven-pile resistance after installation—for 12 bridges along Virginia’s I-64 corridor. The bridges are founded on piles embedded mainly in the Coastal Plain’s Yorktown and St. Mary’s formations, with some piles extending into the Eastover Formation.<br /><br />Researchers analyzed 56 pile dynamic analyzer (PDA) tests, comparing end-of-drive measurements with restrikes conducted from a few hours to 34 days later. CAPWAP analyses separated shaft and end-bearing resistance. In most cases, total resistance increased substantially over time, with observed setup factors commonly around 1.5 to 4 and some higher results. Shaft resistance generally increased more than end-bearing resistance; end-bearing gains were usually modest, except for some precast concrete piles in the St. Mary’s Formation. The data showed no clear distinction in setup between the formations or between broadly fine- and coarse-grained soils. Pile type appeared influential.<br /><br />Using the Skov and Denver empirical relationship, the authors back-calculated setup parameters and proposed separate estimates for steel H-piles and precast prestressed concrete piles. Their analysis suggests that roughly 70% of the estimated setup gain occurs within the first two weeks, with further increases continuing at a slower rate. The estimates are intended to help engineers predict later pile capacity from end-of-drive results and potentially reduce unnecessary pile lengths, sizes, costs, or construction delays.<br /><br />The authors caution that setup is variable and depends on soil conditions, pile type, and elapsed time. Some initial-drive measurements were unreliable because of pile rebound, and empirical estimates did not always match measured capacities. Additional PDA data and refinement of the method are needed before applying the proposed factors beyond comparable Coastal Plain deposits.

Keywords

soil setup

driven pile resistance

Virginia I-64 bridges

pile dynamic analyzer

CAPWAP analysis

shaft resistance

end-bearing resistance

Coastal Plain soils

Skov and Denver relationship

precast concrete piles