Investigation on shear modulus and damping ratio of Algiers marls under cyclic and dynamic loading conditions

A sound knowledge of the dynamic properties of soils is needed to solve several geotechnical engineering problems associated with earthquakes. Here we describe a laboratory investigation performed to measure the dynamic properties of the Plaisancian deposit of marls in the Algiers region using cyclic triaxial tests, cyclic double specimen direct simple shear tests, cyclic torsional shear tests and dynamic resonant column tests. The key parameters governing the nonlinear soil behavior under cyclic/dynamic loading and their relative importance in terms of affecting the dynamic properties of soils, wich are communaly represented by the normalized equivalent shear modulus reduction and damping ratio curves, are illustrated and discussed. We also address the differences in the deduced parameters obtained with different tests, procedures and interpretation criteria. The comparison between test results and empirical or semi-empirical relations for normalized equivalent shear modulus and damping ratio curves highlights a number of limitations and shortcomings of predictive models currently widely used.