The influence of non-plastic fines on pore water pressure generation and undrained shear strength of sand-silt mixtures

An extensive experimental study was undertaken to investigate the influence of non-plastic fines on pore water pressure generation and undrained cyclic shear strength of sand-silt mixtures. For this purpose, stress-controlled undrained cyclic simple shear (CSS) tests were carried out on reconstituted specimens of Ticino silica sand under different combinations of fines content (FC) and global void ratios (e). The applicability of several models suggested in literature for predicting cyclic residual excess pore water pressure generation in non-plastic silty soils was analyzed, and revised correlations for assessing model parameters were proposed. Finally, the study confirmed that the equivalent granular void ratio (e*) is an effective and appropriate parameter for characterizing the behavior of sand with fines up to a threshold value of fines content of sand-silt mixtures, and cyclic resistance ratio (CRR) of the mixtures can be well correlated with e*, irrespective of their fines contents and void ratios.