Independent assessment of toe and skin capacities in near real-time using top and toe instrumentation

The conventional practice of estimating the capacity of deep foundations using dynamic load testing is done by
obtaining data from external sensors that are bolted near the top of the pile. The toe and skin components are
extracted from the total estimated capacity using signal matching analysis with several assumptions. The results of
signal matching analysis are highly dependent on the user performing the analysis and the program utilized.
Therefore, the estimated toe and skin capacities are not known with certainty. Also, in top only instrumentation the
actual condition of pile toe is only approximately deduced from the top instrumentation data. To overcome these
uncertainties, Florida Department of Transportation sponsored research with University of Florida led to the
development of EDC (Embedded Data Collector) with sensors embedded at the pile top and pile toe. Using state-ofthe-
art FDOT (Florida Department of Transportation) method of analysis of the top and toe instrumentation data
collected, it is now possible to independently determine the toe and skin capacity accurately in near real-time. In the
FDOT method Toe capacity is calculated using ‘Energy Conservation’ principle with toe gauge data and, Skin
capacity is calculated using ‘Segmental Skin Friction’ approach with top and toe gauge data as boundary condition.
The benefits of FDOT method analysis using top and toe EDC instrumentations includes a more efficient design,
improved quality, faster construction process. FDOT method of analysis results along with superposition principle to
determine the optimum capacity of piles were demonstrated for a bascule bridge built over the Miami River on state
road 968, Florida, USA where uplift was a critical design aspect of the bridge.