Abstract: The Q3 loess is widely distributed in the northwest of China, and most of them present significant structural characteristics. With the development of the national “The Belt and Road” Initiative, as the northwest loess areas along the silk road will usher in a new tide of construction. The structural deformation characteristics of loess are very complex. In-depth study of the structural damage and deformation characteristics of loess under compression and shearing conditions is of great significance for constructing the constitutive relation of loess in theoretical research and field engineering application. Through the three-axis isotropic compression test and the three-axis shear test, the ball stress damage ratio of the loess structure, the ball stress damage ratio and the shear stress damage ratio are proposed. According to the elastic and plastic strain of the plastic potential line, and its yield function, the damage ratio of loess is introduced to the yield function, and expressed under structural damage. The rationality of selecting the plastic volumetric strain as the hardening parameter is verified. According to the relationship between hardening parameter and the test parameters, damage constitutive model of structural loess under the condition of compression and shear is derived. By comparing the measured stress-strain curves with the calculation from the constitutive model, we can see that the constitutive model can better reflect the structural damage evolution and deformation process of loess under compression and shearing condition.

Key words: structural loess, damage mechanics, damage ratio, yield surface, constitutive model