Experimental Methods and Qualification of the Data

摘要

Extreme care was taken in the design of axial strain measuring devices, lateral total and pore pressure transducers, custom cables and connectors, and specially-stable instrument circuitry, with the result that all instruments performed perfectly over the 2.5-year period that the pile was installed. The need to discriminate small differences in axial loads along the pile at shallow depths in order to establish accurate soil reaction versus displacement (t-z) curves led to the use of static load test data for full-scale calibration of the instruments along the upper half of the embedded length. The resulting calibration data exhibited a degree of linearity better than 0.1 percent. For the instruments along the bottom half of the pile, such extreme precision in the load differences was not required to obtain an equal degree of precision in the calculated values of shear transfer. Exceptional stability was observed among the strain modules, with no discernable drift in the units over the entire 2.5-year period. Variations with time in the residual axial loads along the pile were very regular, and are related to the ongoing vertical consolidation of the upper 80 ft of sediments. Various other comparisons among the data taken with the instruments were made to verify the accuracy and reliability of the load and displacement data that were used to develop design correlations.