The influence of undrained cyclic loading patterns and consolidation states on the deformation features of saturated fine sand over a wide strain range
Abstract 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 a 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 g r curves for shear modulus reduction G G 0 the damping ratio l and Poisson's ratio u with increasing strain were determined. The results of the cyclic axial torsional combined tests showed a close relationship between G 0 g r and u as well as the consolidation state parameters p 0 R 0 a 0 and b 0 The G 0 and g r increased nearly linearly with increasing p 0 and with decreasing a 0 or b 0 The u is strain dependent and increases as the p 0 decreases. Tests indicated that the reduction of G with increasing shear strain g became more pronounced as p 0 increased. The relationship for the G G 0 versus g g r was approximately independent of the cyclic loading patterns and the various values of parameters p 0 R 0 a 0 and b 0 A slight difference is noted between the damping ratios l t and l 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.