Equivalent state parameter dependency on gradation properties of medium sand-fines mixtures

Multiple studies confirm that determining the liquefaction resistance of sand-silt mixtures is more intricate compared to pure sand. Furthermore, it has been observed that the global void ratio fails to accurately predict the behavior of silty sand soils due to the fines particles, which can occupy voids between sand grains without significantly contributing to resisting external forces. To address this, a new parameter called equivalent void ratio (e*) has been proposed to better forecast the response of medium sand-fines mixtures. To investigate this further, a series of compression triaxial tests were conducted on mixtures comprising medium sand with low plastic fines. These mixtures were prepared in the laboratory with an initial relative density and subjected to varying confining pressures. The test results were utilized to assess the undrained shear strength of medium sand-silt mixtures based on the equivalent void ratio (e*) and to establish the equivalent granular steady-state line, which serves as a reference for calculating the equivalent state parameter (psi*). Analysis of the obtained data suggests a correlation between the equivalent void ratio (e*) and the equivalent state parameter (psi*) with the grading characteristics (such as D10, D50, Cu, D10R, D50R, and CUR) of the medium silty sand.