PREDICTION OF FRACTURE FATIGUE PARAMETERS FROM CREEP TESTING OF SOIL CEMENT.
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abstract
When a cement-treated base layer is subjected to repeated stress, inherent microcracks begin to propagate and coalesce from the bottom of the layer and finally cause the layer to fail. In order to identify the rate of fatigue failure of the cement-stabilized base layer, Paris' law, da/dN equals A( DELTA K//m//a//x)**n, can be used. In this research, the parameters, A and n, were predicted by a viscoelastic approach. Uniaxial tensile creep tests were performed, and the creep versus time data were represented by means of the generalized power law, D(t) equals D//0 plus D//2t**m. This power form represents the creep response of soil cement much better than the pure power law, D(t) equals D//1t**m, because of the large initial elastic strain. Schapery's crack growth theory in linear viscoelastic media, based on the classical correspondence principle plus Laplace transform inversion, was utilized to express A and n in terms of measured creep parameters and simple material properties. These predicted parameters were compared with those developed empirically at different cement contents and curing ages. Plots of log A versus n were used to verify the validity of the viscoelastic approach to the fatigue failure criteria.
