Damage evolution and constitutive model of layered yellow sandstone based on energy dissipation

The bedding structure affects the mechanical properties and stability of engineering rock masses. To investigate the influence of bedding angle on the deformation and damage process of rocks, seven uniaxial compression tests of yellow sandstone with different bedding angles of 0 °, 15 °, 30 °, 45 °, 60 °, 75 °, and 90 ° were conducted. Based on the degradation degree of elastic modulus and the evolution characteristics of dissipative energy, the initial bedding damage variable and load damage variable of yellow sandstone were characterized, and the entire evolution process of coupled damage variables was simulated and characterized using logistic functions. The influence of bedding angle on the damage evolution of yellow sandstone was discussed, and a piecewise constitutive model that can simulate the whole deformation process of layered yellow sandstone under uniaxial compression was established by combining the theory of damage mechanics and effective medium theory. The results show that the fracture mode of layered yellow sandstone is closely related to the dip angle of the bedding. When the dip angle is within the range of 0 °~60 °, the main occurrence is splitting tensile failure that cuts through the weak plane of bedding. When the dip angle is 75 ° and 90 °, the rock sample undergoes shear sliding and splitting tensile failure along the weak plane of bedding; The damage evolution curve based on dissipative energy characterization can be divided into four processes: initial no damage, damage initiation, damage acceleration, and damage deceleration termination. The theoretical damage model constructed with the help of logistic functions can effectively simulate and predict the entire damage evolution process of layered yellow sandstone; The ratio of the maximum to minimum initial bedding damage is approximately 1.41, indicating that the bedding dip angle has a significant impact on the initial damage of yellow sandstone; The piecewise constitutive model can describe the whole stress-strain process of layered yellow sandstone under uniaxial compression, and the theoretical model curve is in good agreement with the test data.