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There are several analytical procedures available to predict the soil-pile interaction parameters required for the analysis of a pile-supported foundation subjected to vibratory forces. A procedure for performing a dynamic lateral field test on a single pile is presented. Results of this test are used to verify the adequacy of the assumptions made for the analytic solution and to judge the appropriateness of the soil-pile interaction parameters.
Dynamic lateral-load tests were conducted on eleven steel-pipe piles at three sites in southeastern Michigan. The piles were 324 and 356 mm (12.75 and 14 in.) in diameter, had lengths from 15 to 49 m (50 to 160 ft) long, and were embedded in both cohesive and cohesionless soils. The procedure consisted of attaching a steel-plate mass, vibratory oscillator, and vibration monitoring instrumentation to the head of each pile. The oscillator was then used to drive the soil-pile-mass system at selected force levels through frequencies from 5 to 55 Hz. The dynamic response was recorded on a strip-chart recorder for later evaluation. The data are presented in figures showing frequency versus response amplitude for each oscillator force level.
The soil-pile-mass system was also set into free vibration using the plucking technique. Results of the steady-state vibration testing are compared with the plucking test results on the same pile.
Conventional soil boring and testing methods were used to determine the subsurface soil profile and static soil properties. Dynamic soil properties adjacent to the tested piles were determined using the seismic cross hole and SH refraction (horizontal polarization of the shear wave) techniques.
Because of the way piles are inserted into the soil, the assumed boundary conditions between the soil and pile used in the analytical solutions seldom match the field conditions. This dynamic testing procedure enables the geotechnical engineer to make a judgment as to the adequacy of the assumptions in the analytical model and to make suitable corrections to match the field-observed results.
lateral loads, piles, vibrations, foundations, horizontal oscillation, machine foundations, deep foundations, soil dynamics, soil-structure interaction, load testing, pile foundations
Engineering applications analyst, Bechtel Power Corp., Ann Arbor, Mich.
Professor of civil engineering, The University of Michigan, Ann Arbor, Mich.