A MICROSLIP MODEL FOR THE SEISMIC RESPONSE ANALYSIS OF DRAINED COHESIONLESS SOIL DEPOSITS

Constitutive equations for drained cohesionless soils under triaxial s tress states, based on a microslip model with internal friction, are p roposed and applied to the analysis of the seismic response of soil de posits. The microslips, assumed localized in the discontinuity surface s passing through the particle-to-particle contacts, describe the effe cts of the sliding and rolling between grains of sand. Once the respon se of the model under cyclic shearing stresses and strains superimpose d on the geostatic stress state has been analysed, the constitutive eq uations are applied to a one-dimensional shear model for the dynamic a nalysis of the layered deposits. An application to an instrumented soi l deposit is then developed, the experimental results of which refer t o both strong and weak motion earthquakes; the comparisons between the experimental and theoretical results point out the peculiarities and validity limits of the model. The model here developed may be applied also to the analysis of two- and three-dimensional sites.