Undrained Displacement Behavior of Spread Footings in Clay

The analytical and experimental undrained displacement behavior of spread footings in clay is investigated in this study. Three spread footings ranging in size from 0.76 to 2.74 m were loaded and displaced up to 130 mm into medium stiff to stiff Beaumont clay. Load-displacement curves were determined, and soil displacements below the edge of the largest instrumented footing were measured. The footing displacements were modeled using linear elastic stress distributions and a nonlinear constitutive model calibrated with common in-situ and laboratory tests results. The effect of soil nonlinearity and footing rigidity on soil displacement behavior was also investigated. Results show that the linear elastic stress distributions used in a nonlinear constitutive setting resulted in very good prediction of undrained displacements at the footing center. Displacements at the edge of the footing were less well predicted. Regardless of the assumption of footing rigidity, when nonlinear, in-situ stress-dependent behavior is modeled, realistic concentrations of displacement towards the footing boundaries are observed.