Stress–strain Behavior of Silt Sand Soil Under Isotropically Consolidated Drained Conditions by Principal Stress Direction and Intermediate Stress Coefficient Parameters

This study investigated the impact of major principal stress direction angle (α) and intermediate principal stress coefficient (b) on the stress–strain behavior of silt sand soil through directional shear tests under isotropically consolidated drained conditions. Analyzing octahedral stress–strain relationships, shear stress–strain behaviors, radial and circumferential strains, shear stress ratios, and non-coaxial characteristics, findings show that both b and α significantly influence strain components with radial strain remaining stable and circumferential strain being dependent on both factors. Anisotropy in circumferential strain is notably affected by α and b, while radial strain transitions from tensile to compressive states by increasing b values. Initial loading stages exhibit similar characteristics, but it increased anisotropic with shear stress particularly at b = 0.5 and b = 1. Shear strength is notably influenced by b and α, with peak shear stress exhibiting direct proportionality to α angles between 0 and 45°, and an inverted relationship beyond 45°. Material strength is significantly impacted by stress orientation with pronounced non-coaxial behavior observed at angles other than 0°, 45°, and 90°. These findings emphasize the intricate relationship between stress coefficients and material behavior providing significant insights into silt sand soil responses under varying stress conditions.