Abstract: Constitutive model of rock damage under loading and unloading is the key to predict the long-term stability of pressure storage tank. Since pressure on surrounding rock changes repeatedly, few constitutive models can be applied at present. The micro-unit strength of rock obeys the distortion energy strength and the Weibull random distribution. In the light of this, we present a damage constitutive model which could describe the staged loading and unloading of rocks. Furthermore, we verified the constitutive model by experiments, analyzed the sensitivity of constitutive parameters according to test data, determined the physical significance of parameters and selected parameters which could reflect the staged loading and unloading. The physical meaning of damage constitutive model parameters is clear and easy to fit, suitable for practical engineering.

Key words: rock mechanics, distortion energy theory, Weibull random distribution, staged loading and unloading, constitutive model