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Foundation conditions are studied for a series of apartment buildings in a shore area reclaimed from the Nakdong River estuary delta west of Busan, South Korea, in full-scale field tests on two 600 mm, post-driving grouted, concrete cylinder piles instrumented with strain gages, driven through compressible layers and a short distance into underlying dense sand at depths of 56 m (Shinho) and 35 m (Myeongji). One test pile was provided with an O-cell so that after an initial O-cell test, a subsequent head-down test only affected pile shaft resistance. The purpose was to evaluate drivability of the piles, magnitude of the drag load due to consolidating soils, and potential settlement (downdrag) of the piled foundations. Early in the study, it became apparent that the internal process of heating and cooling of the grout during the hydration process and swelling from absorption of water affected the strain records and the assessment of residual load in the test piles during the wait time before the static loading test. The paper reports the measurements, analyses, and method for determining residual load, strain-dependent modulus of test piles, and actual load distribution in the test piles. The results are correlated to cone penetration test (CPTU) sounding data and effective stress analysis. [ABSTRACT FROM AUTHOR]

The development of strain in two 31 and 56 m long instrumented postdriving grouted cylinder piles at a site west of Busan, South Korea, were monitored during 200 days after construction, whereupon a static loading test was performed. Initial strain measurements showed unexpected elongation of the pile, probably due to swelling from absorption of water but as the soil reconsolidated, the elongation changed into shortening, probably due to imposed residual load in the pile. The resulting compression of the pile eventually offset the swelling of the pile. To investigate the cause of the strain changes more closely and enhance the evaluation of the field data, two short pile pieces were prepared and placed free-standing above ground in an outside laboratory. One piece was from a cylinder pile of which central void was grouted and one was made up by grouting inside a temporary casing. The monitoring showed that the short pieces appeared first to shorten and then to elongate due to the heating and cooling from the hydration process. When strains and temperature had stabilized 150 days after start of the study, both pieces were submerged to introduce swelling of the concrete. For the first 100 days after submerging, the swelling strains in both short pieces amounted to 100 μ[variant_greek_epsilon]. Seven hundred days after submersion, the total swelling strains were 150 and 250 μ[variant_greek_epsilon]. [ABSTRACT FROM AUTHOR]