Anisotropic Damage Model of Soft and Hard Composite Rock and Experimental Verification

Abstract

Abstract In order to derive the anisotropic damage model of soft and hard composite rock and to study the influence law of damage on the deterioration degree of material mechanical parameters in different directions, the transversely isotropic elastic constitutive equation was corrected by two sets of damage variables in the local coordinate system of bedding plane. By coordinate transformation, an effective stress–strain relationship in the global coordinate system was formed. The rationality of the damage model was verified by the results of uniaxial compression test. The results show that (1) The damage of soft and hard composite rock has transversely isotropic characteristics. (2) The change trend of damage variables varying with strain is closely related to each stage of the damage process; at the same strain level, the damage variables increase first and then decrease with the increase of the bedding plane’s dip angle (0°~90°) and have a good corresponding relation with the damage model. (3) The strength and deformation parameters calculated by the damage model of soft and hard composite rock can reflect the test results well and have obvious anisotropy. The calculated curves before failure are also consistent with the experimental results. (4) Through the damage model, the stress–strain relationship at each dip angle can be determined by the two sets of deformation parameters for the bedding plane’s dip angles of 0° and 90°. Because the damage deterioration effect during loading process is considered, the mechanical behavior of the specimens after failure can be predicted, which has some guiding significance for the experimental research, theoretical calculation, and engineering construction based on soft and hard composite rock.