Experimental Study of Directional Shear of Q₂ in Situ Loess Considering the Direction of Principal Stress

In order to study the effect of principal stress deflection angle on the strength and deformation characteristics of Q₂ in-situ loess under directional shear. The deformation and strength characteristics of Q₂ in-situ loess under directional shear loading were researched, and the in-situ properties in comparison with remodeled loess were analyzed. The effect of structural properties of loess on shear properties and non-coaxial properties was analyzed in comparison with remodeled loess. The test shows that due to the difference of internal structural properties of in-situ loess, when the main stress deflection angle α is between 0 and 15°, the directional angle of strain increment gradually increases with the increase of α, and the non-coaxial property increases; when the main stress deflection angle α is between 30° and 90°, the directional angle of strain increment gradually decreases with the increase of α, and the non-coaxial property decreases. The overall trend is that it first strengthens and then weakens. At the same time, because the structural properties within the in-situ loess are not destroyed before the peak strength, the total generalized strain value when reaching the damage is small, and the generalized shear strain value when reaching the peak strength is also small, usually about 2% reaching the peak strength, and then the damage occurs rapidly with larger deformation.