Experimental study on undrained monotonic and cyclic behavior of sandy silts with different fines content

The presence of fine particles can change the microstructure of sandy silts and thus affect their mechanical properties. In this study, a series of undrained triaxial tests was conducted to investigate the monotonic and cyclic behavior of sandy silts with fines content (FC) of 60%, 76%, and 92%. The different effective confining pressures (o3' = 40, 60, 80, 100, 120, and 140 kPa) and cyclic stress ratios (CSR, od/2o'od/2o3' = 0.12, 0.18, 0.24, and 0.36) were considered in the experiment study. The research results showed that the undrained shear strength of sandy silts increased significantly with the increase of o 3', but decreased with the increase of FC. A larger amplitude and rate of double amplitude axial strain and excess pore water pressure ratio were observed as the CSR increased. The liquefaction resistance of the sandy silts initially decreased and then increased with the increasing o 3'. The lowest liquefaction resistance was found in the cases of o 3' = 100 kPa. An increase in FC can delay the generation of excess pore water pressure and enhance the liquefaction resistance of sandy silts under the cyclic loading. Two quantitative relationships between the number of loading cycles to failure and the FC were established through nonlinear surface fitting, respectively, considering the different cyclic stress ratios and effective confining pressures. The research results can provide a reference for the liquefaction treatment of sandy silt foundations.