FDOT Method of Independent Separation of Tip and Skin Capacities of Driven Concrete Pile with Embedded Sensors-Paper

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The paper presents the Florida Department of Transportation (FDOT) method for independently estimating the static tip and skin resistance of driven concrete piles. Conventional dynamic testing generally derives capacity from a single hammer blow, but pile-tip and shaft resistance are not fully mobilized at the same time. Combining both estimates from one blow can therefore understate or misrepresent the pile’s optimum capacity.<br /><br />The method uses Embedded Data Collectors (EDCs): sensors installed near the pile top and tip that record strain and acceleration during driving and transmit data wirelessly. Tip measurements are analyzed using force and energy equilibrium to estimate static tip resistance. Measurements from the top and tip are also used in a one-dimensional, segmented pile-soil model to calculate skin friction independently for each pile segment.<br /><br />Because peak tip and skin resistance occur at different stages, the method selects appropriate blows: typically an end-of-initial-driving (EOID) blow for tip resistance and a beginning-of-restrike (BOR) blow for skin resistance. Their values are then superimposed to estimate total capacity. This approach is intended to address strain incompatibility between tip and shaft mobilization and can also help quantify shaft-resistance losses associated with jetting or preforming.<br /><br />A field example at Caminada Bay, Louisiana, reported 25 kips of tip resistance from an EOID blow and 531 kips of skin resistance from a restrike blow, for a combined estimate of 556 kips, compared with a static load-test capacity of 625 kips.<br /><br />The authors argue that embedded instrumentation enables real-time monitoring and practical testing of every pile, while avoiding external wiring and reducing the need for workers to climb pile leads. Measured driving stresses can inform cushion changes, and continuous testing may improve construction efficiency, safety, and cost control.

Keywords

Florida Department of Transportation

FDOT

driven concrete piles

static tip resistance

skin resistance

embedded data collectors

pile capacity estimation

dynamic pile testing

restrike blow

one-dimensional pile-soil model