THE INFLUENCE OF A STEEL CASING ON THE AXIAL CAPACITY OF A DRILLED SHAFT

A series of field load tests were performed to investigate the effects on the axial capacity of drilled shafts when casings could not be pulled. The tests show that leaving casing in place is detrimental, but grouting proved an effective remedial measure when the casing was placed in an oversized excavation. Even though grouting was found to improve the capacity of a shaft where casing was left in place, procedures should bed used in the field that will insure that casing will be removed. Shafts cast in the normal manner perform better than do shafts where casing has been grouted. Useful data were obtained on the distribution of axial load from drilled shafts to the supporting soil. (FHWA)