Elastic shear modulus variations during undrained cyclic loading and subsequent reconsolidation of saturated sandy soil

To evaluate the variations in the elastic shear modulus G(0) of saturated sandy soil during consolidation, undrained cyclic loading and reconsolidation, we performed a series of multiple-phased triaxial tests with measurements of shear wave velocity on specimens having different dry densities. At the same isotropic effective stress, the G(0) value during undrained cyclic loading became smaller than that during initial consolidation. For the same effective stress parameter that was found to be relevant to the isotropic and anisotropic stress states, the G(0) value at an identical effective stress parameter at isotropic and anisotropic stress states during undrained cyclic loading decreases similarly with an increase in the previous strain amplitude. By reconsolidation to the original effective stress state, the G(0) value increased partly due to recovery from the shear-induced damage and partly due to a decrease in the void ratio. The effects of the former factor decreased as the specimen became denser, while the effects of the latter factor increased as the specimen became looser. As a result, compared with the initial value at the end of initial consolidation, the G(0) value after reconsolidation of the same specimen became significantly smaller with dense specimens while it became significantly larger with loose specimens.