Full-scale field load testing of long drilled shafts with enlarged base constructed in marine sediment

Abstract

ABSTRACTLong drilled shafts with enlarged bases are generally used to transfer heavy loads from superstructures to the underlying soils. Due to the large slenderness ratio, the load transfer mechanism for these long enlarged base-drilled shafts differs from that of a conventional drilled shaft. This paper presents field-instrumented, full-scale load tests on long drilled shafts longer than 58 m, including one straight and two enlarged base-drilled shafts in marine sediment. The field test results show that compared with straight shafts, the use of an enlarged base increases both toe resistance and shaft resistance. The drilled shafts with enlarged bases have higher load-bearing capacity. The shaft resistance and toe resistance were not simultaneously mobilized. The bottom sediment under the shaft toe has a significant influence on toe resistance and shaft resistance. Shafts having bottom sediment with a relatively large thickness exhibited lower shaft and toe resistance. Thus, the bottom sediment thickness should be strictly controlled.