Deterioration characteristics and damage constitutive model of granite-shotcrete under acid corrosion cycle conditions

Abstract

The acidic groundwater environment will cause the degradation of tunnel and underground engineering structures, posing a severe threat to their durability and load-bearing performance. This paper analyzed the mechanical properties and microstructural changes of the specimens under the action of the acid cycle by carrying out mechanical, acoustic emission (AE) and scanning electron microscopy (SEM) tests. The evolution rules of elastic wave velocity and acoustic emission characteristic parameters were discussed. A damage constitutive model was established based on the Weibull strength theory. The results show that the specimen interface split tensile stress-strain curve is divided into elastic, interface softening and debonding failure stages. After 20 cycles, the peak strength and elastic modulus of the specimen decreased by 55.63% and 71.43%, respectively. The porosity calculated based on longitudinal wave velocity and mass changes can better explain the changes in the microstructure of the specimen. The fractal dimension value associated with the longitudinal wave velocity of the specimen and the ringing count shows a negative proportional relationship, and its proportional coefficient is 329.29. The stress-strain theoretical curve of the established damage constitutive model has a high degree of agreement with the test curve. The research results can provide an essential reference for disaster prevention and control of tunnels and underground projects in acidic groundwater areas.