Shear stress-strain relationships and anisotropy in silty soil: The role of principal stress rotation

This study uses a hollow cylindrical apparatus to explore the effects of principal stress rotation on saturated silty soil, focusing on the static characteristics affected by cycle counts, intermediate principal stress coefficient (b), and rotational angle (α). As the principal stress axis rotates, strain fluctuations decrease and stabilize, with consistent strain trends observed across various b values. Anisotropy appears around 60° during the first cycle, significantly impacting radial strain while torsional shear strain remains less affected. Distinct hysteresis loops in shear stress-strain relationships reveal initial unclosed forms due to plastic strain accumulation, transitioning to closed loops with increased cycling, and showing noticeable variations in shear stiffness. As b values rise, stiffness degrades, influenced by both b values and a angles. Volumetric strain shows a linear increase for two cycles before decelerating, with b=1 demonstrating anisotropy at 60° and other values at 90°. Minimal contraction occurs for b=0 after the tenth cycle, while b=0.5 sees significant volume reduction. Higher b values also reduce non-coaxial behavior, linked to the initial principal stress orientation. These findings enhance the understanding of silty soil behavior under stress rotation, offering valuable insights for geotechnical engineering applications.