Nonlinear rocking stiffness of foundations

The response of surface foundations to large overturning moments is studied under undrained conditions. Rigid circular, strip, and rectangular footings of various aspect ratios are considered, with the soil modeled as an inelastic homogeneous deposit, characterized by an elastic (small-strain) shear modulus Go, an undrained shear strength Su, and a G/Go versus γ curve appropriate for medium-plasticity clays. Three stages of foundation performance, ranging from the initial elastic fully-bonded response, to the nearly-elastic but nonlinear response with the foundation partially detaching and uplifting from the soil, and finally to the ultimate stage where full mobilization of soil bearing failure mechanisms develop. Simple to use formulas or charts are developed for all stages of response in terms of dimensionless parameters, prominent among which is the static factor of safety against bearing-capacity failure under purely-vertical loading.

► The response of surface foundations to large overturning moments is studied.
► Rigid circular, strip, and rectangular footings of various aspect ratios are considered.
► Simple to use formulas and/or charts are developed for all stages of response.