Shaft Resistance of Drilled Shafts in Clay

Abstract

Thecurrentstudyexaminesandquantifiesthelimitshaftresistanceofdrilledshaftsinstalledinclaythrough finite-elementanalyses that use an advanced two-surface-plasticity constitutive model for clay. The clay constitutive model used in this study reproduces the mechan- ical responseofclaysundermultiaxial loadingconditions,predictsbothdrainedandundrainedbehavioratsmallandlargestrains,andcaptures the drop in strength toward a residual value at very large shear strains. One-dimensional finite-element analyses are performed to simulate the essential stages of the installation and loading of drilled shafts in clay for different initial stresses, different overconsolidation ratios, and dif- ferent values of the difference between the critical-state and the minimum residual friction angles. On the basis of these simulations, equations for the shaft friction coefficient are proposed that can be used in the calculation of the shaft resistance of drilled shafts in clay. Predictions using theproposedequationscomparewellwiththedataderivedfromdifferent fieldpileloadtestsondrilledshafts.DOI:10.1061/(ASCE)GT.1943- 5606.0000803. © 2013 American Society of Civil Engineers. CE Database subject headings: Drilled shafts; Piles; Clays; Numerical models; Plasticity; Finite element method; Constitutive models. Author keywords: Drilled shaft; Nondisplacement piles; Shaft capacity; Clay; Numerical modeling and analysis; Two-surface plasticity.