Load Test Correlation utilizing embedded sensors for dynamic and static load testing.-PPT Presentation

PPT Presentation

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The presentation compares static load tests (SLT) and dynamic load tests (DLT) on two 36-inch-diameter drilled shafts in similar clay and silty sand conditions. Both shafts had strain gauges at five depths and were tested to failure. Maximum SLT loads were 1,125 kips at Location 1 and 1,280 kips at Location 3. Field DLT results reported capacities of 634 and 915 kips, respectively.<br /><br />Embedded strain measurements helped distinguish shaft resistance from toe resistance—an important benefit because conventional signal matching has limited resolution near the pile toe, particularly with heavily cushioned impacts. The Location 1 analysis estimated 634 kips total resistance, including 529 kips of shaft resistance and 105 kips of end bearing. At Location 3, the signal-matching analysis estimated about 969 kips, divided into roughly 679 kips of shaft resistance and 290 kips of end bearing.<br /><br />The results also show that interpretation depends on accurately modeling pile impedance and cross-sectional area. Strain must be converted to force using the assumed area and modulus; at Location 3, treating the shaft as uniform would have produced a force estimate 27% lower than accounting for the enlarged toe indicated by thermal integrity profiling (TIP). Integrity-test results and construction information can therefore improve dynamic-test interpretation.<br /><br />The authors caution that testing both piles to failure may have altered their resistance profiles. Large SLT displacements and creep cannot be assessed by a later DLT, making direct comparisons difficult. Overall, multiple measurement types can improve capacity estimates, but only when their assumptions and limitations are carefully considered.

Keywords

static load test

dynamic load test

drilled shafts

strain gauges

shaft resistance

toe resistance

signal matching

end bearing

pile impedance

thermal integrity profiling