Load Distribution for a Drilled Shaft in Clay Shale: Fid-Bau Portal

Load Distribution for a Drilled Shaft in Clay Shale

V. N. Vijayvergiya / W. R. Hudson / L. C. Reese

Large diameter drilled shafts are used extensively to support axial loads; however, the behavior of these shafts is not well understood. Questions arising with regard to the design of such shafts concern the interaction of wet concrete with soil, the possible shrinkage of concrete on drying, the eventual earth pressure at the interface of the shaft and the supporting soil, and the mechanics of the interaction of the shaft with the foundation. This report describes a comprehensive investigation aimed at gaining more information related to the above questions. A 30-inch by 28.5-foot drilled shaft was instrumented and tested under axial load. The instruments were read for a series of load increments. The shaft was tested five times with loads to 990 tons. The test data were analyzed to obtain curves giving distribution of axial load along the shaft as a function of depth and curves showing load transfer at various depths as a function of downward movement of the shaft at that depth. Results were correlated with soil properties obtained from Texas cone penetrometer tests. A tentative design procedure is proposed and load-settlement curves computed by this procedure compared with observed curves. (Author)