The influence of undrained cyclic loading patterns and consolidation states on the deformation features of saturated fine sand over a wide strain range

Undrained cyclic loading patterns and consolidation states can significantly affect the deformation features of medium-dense saturated fine-grained sand. A series of undrained cyclic loading tests with different consolidation states, i.e., various mean effective consolidation stresses (p(0)), principal stress direction angles (alpha(0)), ratios (R-0) of major and minor principal stresses, and relative magnitudes of intermediate principal stress (b(0)), were performed on saturated micaceous fine sand specimens with a relative density of 50% corresponding to a wide strain range in the order of 10(-5) to 10(-2). The patterns of cyclic axial, torsional, and axial-torsional combined loadings were applied in a hollow cylinder apparatus. The small-strain shear modulus G(0), the reference shear strain gamma(r), curves for shear modulus reduction G/G(0), the damping ratio lambda and Poisson's ratio nu with increasing strain were determined. The results of the cyclic axial-torsional combined tests showed a close relationship between G(0), gamma(r), and nu as well as the consolidation state parameters p(0), R-0, alpha(0), and b(0). The G(0) and gamma(r) increased nearly linearly with increasing P-0 and with decreasing alpha(0) or b(0). The nu is strain dependent and increases as the p(0) decreases. Tests indicated that the reduction of G with increasing shear strain gamma became more pronounced as p(0) increased. The relationship for the G/G(0) versus gamma/gamma(r) was approximately independent of the cyclic loading patterns and the various values of parameters p(0), R-0, alpha(0), and b(0). A slight difference is noted between the damping ratios lambda(t) and lambda(z), corresponding to vertical and torsional deformations. An empirical model was proposed for the dependence of the increase in damping ratio characteristics on the deviatoric strain. (C) 2016 Elsevier B.V. All rights reserved.