Impact of Particle Characteristics on the Static Liquefaction of Jhelum Riverbed Sand

The undrained shearing behavior of the Jhelum Riverbed sands and the effect of fines content on their overall response and their static liquefaction potential are still elusive. In this context, the present study aims to understand the undrained shearing response and static liquefaction potential of Jhelum riverbed sands through a series of isotropically consolidated undrained compression (CIUC) triaxial tests. The effect of sand type and fines content were established through CIUC triaxial tests conducted on clean sands obtained from three different locations (Khanabal, Rajbagh, and Sopore) along the Jhelum River and sand-silt mixtures. Results showed that volumetric compressibility (m(v)) decreased by 67, 65, and 46% as the relative density increased from 15 to 50% for KS, RS, and SS sands, respectively. Compared to clean sands, an increase of 23 and 15% in mv was observed with the addition of 7 and 14% nonplastic fines, respectively. An increase in the undrained shearing resistance by factors of 2.12, 3.08, and 1.98 for KS, RS, and SS, respectively, is observed as the relative density increases from 15 to 50%. An increase in undrained strength by 79.2% is observed when the initial effective confining pressure (p(i)') is increased from 50 to 150 kPa. It was also observed that Jhelum sands follow normal behavior of increasing contractile tendency as p(i)' increased from 50 to 150 kPa. Specimens with larger mean grain diameter (D-50) and lower coefficient of uniformity (C-U) values exhibited higher undrained strength as well as higher liquefaction resistance. Higher roundness and sphericity values facilitate a higher generation of excess pore water pressure, resulting in higher liquefaction potential. With the addition of non-plastic fines, the Sopore Sand-silt mixture exhibited higher liquefaction potential, more strain-softening behavior, and higher excess pore pressure, resulting in 83 and 51% reduction in p(i)' at 7 and 14% fines content, respectively. A unique critical state line in q - p' space is observed for sand silt mixtures.