DFI Journal - The Journal of the Deep Foundations Institute

Volume 3, Issue 2, June 2009

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A Comparison of Open Drilled Shafts to TemporarilyCased Drilled Shafts in Clay Soil (Vol. 3 No. 2)

W. Tom Witherspoon, Ph.D., P.E.


Many Engineers are skeptical and cautious about skin friction factors for the portion of drilled piers where temporary casing is used. This has led Texas engineers in many cases to eliminate skin friction values for the cased section, which necessitates deepening the drilled shaft to compensate for the loss in the cased section. This paper has provided field test data that supports inclusion of skin friction in the temporarily cased hole section as a contributing factor in total axial capacity as comparable to open hole shafts of the same diameter. Reasons for the resultant friction values are provided including; remolding of the cased clay section and the increased pier circumference necessitated by the oversized casing required for adherence to the engineers shaft diameter specification."

Cased Shafts, Side Friction, Skin Friction