Constitutive Model of Concrete Creep Damage Considering the Deterioration of Creep Parameters

The MTS815.03 rock test system is used to carry out mechanical property and triaxial compression creep tests on concrete specimens of the same specification under different confining pressure conditions to study the creep characteristics of concrete structures in deep high-stress level areas. The relationship between the creep strain rate of the concrete specimen and the stress level and the creep characteristics of the concrete specimen in the high-stress level area are analyzed. Based on the establishment of a creep damage model in the high-stress level zone of a concrete specimen, a method for determining creep parameters is proposed on the basis of the characteristics of the creep test curve. The degradation law of creep parameters under different stress levels is analyzed, and the relationship between creep parameters and stress is constructed. Finally, the expressions between each creep parameter and stress are substituted into the creep damage model, and an improved creep damage model is obtained. The correctness of the established model is verified by comparing the test curve and the model curve. Result shows that the agreement between the established creep model curve and the accelerated test curve is higher than that between the traditional Nishihara model curve and the accelerated test curve. The established creep damage creep model can be used to predict the deformation trend of surrounding concrete over time after chamber or tunnel excavation and provide theoretical basis for concrete support and lining construction.