Assessment of K₀ correlation to strength for granular materials

The coefficient of lateral stress at rest K₀ is a state soil variable, yet is well correlated to strength. As different types of friction angles can be defined, it is important to examine the applicability of K ₀-strength correlation and further clarify the mechanism of K ₀-stress state. In this study, the values of K₀ were experimentally investigated for different types of granular materials, focusing on its correlation to material strength and the effect of particle shape and surface roughness. For this purpose, laboratory tests were conducted to directly measure K₀ of natural sand, spherically shaped glass bead, and surface-etched glass bead packings under various stress and soil conditions. Triaxial and other basic property tests were also conducted to characterize the test granular materials. It was revealed that the effect of material density on K₀ differed depending on the stress history whereas the effect of particle surface roughness, within the range considered in this study, was relatively small. Test results highlight that the values of the friction angle employed into Jaky's K₀ equation to match measured K₀ values are not unique, showing a statedependent aspect. Inter-particle stress analysis was introduced to assess the correlation of K₀ to the friction angle as postulated by Jaky's K0 equation.