Experimental investigation on anisotropic behavior of Yellow River silt with different initial water contents and confining pressures

The mechanical behavior of Yellow River silt is influenced by its initial water content w0 and confining pressure p. Directional shear tests were performed on specimens with seven w0 values (4% to 24%) under three confining pressures (40, 60, 80 kPa) to investigate their effects on deformation, strength, and non-coaxial characteristics. Results show that at constant w0, peak deviator stress increases with p. The octahedral shear stress at a given strain first rises and then falls with increasing w0, peaking at 14%. Similarly, under constant p, the failure strength shows a non-monotonic relationship with w0, reaching a maximum at the critical w0 of 14%. Strength is relatively low for w0 < 8% and decreases markedly for w0 > 24%, while consistently increasing with higher p. The non-coaxial angle displays significant anisotropy with w0, decreasing initially before increasing. Consequently, engineering practice must account for the significantly reduced strength under low (24%) water content and low confining pressure. This study clarifies the mechanical behavior of Yellow River silt under varying conditions, providing a theoretical basis for engineering and disaster mitigation in the region.