Creep characteristics and deterioration mechanism of limestone under stress and water-rock coupling

The deterioration of rock mass in the riparian zone of the Three Gorges Reservoir area has always been a hot topic in related fields. In view of the deterioration of rock mass in the hydro-fluctuation belt of carbonate rock bank slope in the Three Gorges Reservoir area, the simulation of the coupling process between the gravity of overlying strata and the periodic fluctuation of reservoir water level is mainly considered. The creep test and microstructure test of limestone in the hydro-fluctuation belt under the coupling of stress and water-rock are designed and carried out to analyze its creep characteristics and deterioration mechanism. The results indicate that: (1) During the creep test of limestone under the coupling effect of stress and water-rock, the creep deformation characteristics of limestone samples gradually increase with the increase of axial stress level and water-rock interaction period. (2) Under the stress level R≤0.75, the deformation tends to be stable after the sample undergoes a short water-rock cycle, and the higher the stress level, the longer the water-rock cycle through which the deformation reaches stability ; under the condition of R≥0.8, the sample finally fails, and the higher the stress level, the shorter the water-rock cycle experienced by the deformation and failure. (3) The test results of limestone microstructure show that under the coupling of stress and water-rock, the internal structure of limestone samples gradually deteriorates, the voids gradually increase, and the structure gradually loosens. (4) The deterioration process of limestone samples is controlled by the cyclic promoting effect among water-rock interaction damage, crack propagation and stress state adjustment. The relevant research results can provide theoretical support for the long-term deformation stability analysis of reservoir bank slope.