Insight into the Effect of Granulometric Characteristics on the Static Liquefaction Susceptibility of Silty Sand Soils

Silty sands are the most common type of soil that is involved in monotonic or dynamic loading induced liquefaction. It is associated with a sudden drop of the shear strength of the soil leading to important damages to civil engineering and hydraulics structures. Therefore, it is of great importance to identify the influencing parameters on the liquefaction of soils for the purpose to develop design strategies and therefore mitigate earthquake damages due to liquefaction phenomena. Published literature indicates that particle shape and gradation are the most important parameters that would affect the liquefaction behavior of granular sandy soils. For this purpose, a series of undrained compression triaxial tests were carried out on reconstituted Chlef sand (Algeria) and Fontainebleau sand (France) samples with low plastic fines ranging from 0 to 40 % and initial relative density (D_r = 52 %) to study the liquefaction susceptibility of these soils. All the samples under study were subjected to an initial confining pressure of (\(\upsigma_{c}^{'}\) = 100 kPa). The evaluation of the obtained data indicates that the gradation and particle shape have a significant influence on the undrained shear strength (liquefaction resistance) of different silty sand soils under study. Moreover, test results confirm the existence of simple correlations between liquefaction resistance and different grading characteristics (D₁₀, D₃₀, D₅₀, D₆₀, and C_u) of the soils under consideration. New soil granulometric ratios (D_10R = D_10sand/D_10mixture , D_50R = D_50sand/D_50mixture, and C_UR = C_usand/C_umixture) were introduced to discuss the sand–silt mixture liquefaction resistance susceptibility response. The used grading characteristics ratios (D_10R, D_50R and C_UR) appear as pertinent parameters to predict the undrained shear strength response of the sand–silt mixtures for soil gradation under study.