The effect of particle shape and bedding angle on mechanical properties of Ili loess under low matric suction

Through extensive laboratory experiments on unsaturated soils, it has been discovered that particle shape and matric suction significantly influence their mechanical properties. Prior studies have typically examined these factors individually and from a macroscopic perspective. In this study, the aspect ratio is utilized as a representative parameter for particle shape. Employing the Hill constitutive model, a series of triaxial shear numerical experiments of simulations on unsaturated soil were conducted. The results indicate a non-linear relationship between peak deviator stress and aspect ratio, with peak deviator stress initially increasing, then decreasing, and reaching its maximum at an aspect ratio of 1.2. The patterns observed in friction angle, cohesion, and critical stress ratio in relation to aspect ratio mirror those seen in peak deviator stress, with the friction angle exhibiting fluctuations as the particle aspect ratio increases. At a matric suction of 0 kPa, changes in particle shape have a negligible impact on mechanical properties. However, as matric suction increases, the volumetric strain’s dilatancy turning point is advanced, and the effect of particle shape becomes progressively more pronounced. Under varying conditions of particle shape and matric suction, the alteration in bedding angle affects the peak deviator stress and stress ratio, albeit the extent of this influence is limited.