Stress-strain relationship and damage constitutive model of wet concrete under uniaxial compression

The deformation and damage of wet shotcrete under geostress in deep mines is a common issue. To better understand the damage characteristics of rock deformation rates on wet shotcrete, uniaxial compression tests were conducted using an RMT-150 C press with five loading rates. Based on the damage mechanics theory, a segmental damage constitutive model was established, which defined the elastic modulus as the damage variable and considered the loading rate. The research findings indicate that the relationship between the compressive strength and elasticity modulus of wet concrete, as well as the loading rate, can be described by quadratic polynomial functions. The elasticity modulus and compressive strength increase slowly when the loading rate exceeds 0.1 mm/s. Additionally, the compressive strength is directly proportional to the elasticity modulus. When wet shotcrete reaches its maximum stress, a higher loading rate results in a faster damage value. However, exceeding the maximum stress drastically reduces the damage value. The relationship between the damage value D and axial strain is represented by a quadratic polynomial function. Although the deformation capacity of concrete increases slightly with an increase in loading rate, the effect is minimal. A segmental damage constitutive model, which considers the loading rate and uses the elastic modulus to define damage variables, has been developed based on the stress-strain curve of wet concrete. The accuracy of the model was verified by comparing theoretical and measured values. The theoretical model can serve as a useful reference for the design of wet shotcrete support.