Degradation mechanism of limestone and time-varying pile capacity assessment in bank slopes under dynamic erosion of CO2 solution

The dynamic erosion effect of the corrosive medium formed by aqueous solution and CO2 gas on rock will lead to the decline of the mechanical properties of rock and seriously threaten the long-term stability and durability of rock mass in the reservoir area. In this paper, a dynamic erosion test method of CO2 solution on rock mass is proposed to study the deterioration effect of CO2 solution on rock, based on the gas–liquid cycle. A total of 210 limestone samples were tested under various dynamic erosion cycles (0, 5, 10, 15, 20, 25, and 30 cycles). A systematic analysis of key physical properties related to the degradation behavior of rock (Young's modulus, uniaxial compressive strength, tensile strength, shear strength, cohesion, and internal friction angle) was performed. Additionally, the changes in dissipated energy, fractal dimension, and micro-pore evolution during the solution erosion process were examined. The results indicate that with the increase in erosion cycles, the mechanical parameters of the samples gradually decreased, while both the proportion of dissipated energy and the fractal dimension of fragmentation increased nonlinearly by 29.58% and decreased by 9.95%, respectively. The porosity of the samples increased from 0.04% to 6.89%, and their multifractal spectrum gradually shifted to the right, indicating the development of internal pores and decreased microscopic structural stability. Finally, a limit analysis method for time-varying bearing capacity analysis of limestone pile foundation was established to analyze the time-varying evolution characteristics of pile capacity based on the deterioration effect of solution on rock.