Abstract: In order to improve the rock damage constitutive model and parameter determination method under high temperature, based on the effective stress theory, the Weibull distribution function is introduced. Under the condition that the micro-element strength obeys the Hoek-brown criterion, the influence of residual strength is considered, the damage variables are modified, the damage correction coefficient is introduced, and a statistical constitutive model that can reflect the damage characteristics of rocks under high-temperature action is established. Considering the damage threshold factor in the rock damage process, the present constitutive model takes the form of a piecewise function. The conventional mechanical parameters are obtained by testing. Based on the process of solving the parameters of the constitutive model, the values of the constitutive model parameters are determined and the relationship between the values of the model parameters and the temperature is fitted. Finally, the theoretical curve of the model is verified. The results show that the theoretical curve of the proposed statistical damage constitutive model for high-temperature rocks has a good similarity with the test curve, and it is closer to the test curve and reflects the reasonableness of the constitutive model. At the same time, the theoretical curve of the model has a high degree of coincidence with the triaxial test curve, which indicates that the constitutive model can reflect the characteristics of the full stress-strain curve of the rock and can reflect the applicability of the model. The model provides a reference for rock strength estimation and rock thermal damage softening.

Key words: high temperature, piecewise function, model parameters, Weibull distribution function, Hoek Brown criterion