This paper describes the third of a series of six shaking table experiments conducted as part of ongoing research to evaluate the accuracy and applicability of the Newmark (1965) procedure for computing seismically induced deformation in slopes. A cohesive model slope was shaken by two identical test motions in succession, mimicking a situation that commonly occurs when a preexisting landslide is subjected to strong earthquake shaking. Back analyses of the tests showed that the Newmark (1965) formulation provided moderately accurate estimates of the measured permanent deformations (within 40% to 85% of the maximum measured displacement). The accuracy of the Newmark (1965) formulation was greatest when displacement-dependent degrading yield acceleration was used to model the soil’s transition from peak to residual shear strength. The Newmark analyses were most reliable for the second test that experienced relatively large deformations, and thus where the sliding resistance was controlled by post-peak to residual strength
