The deterioration of rocks on reservoir bank slopes under flowing water conditions can seriously compromise slope stability. Meticulously exploring the macro-mechanical properties and microstructures of rocks under dynamic water scouring conditions is of great significance for disaster prevention and control in reservoir areas. To simulate the water flow environment of reservoir bank slopes

a rock scour resistance test device was designed. Taking sandstone as the research object

three conditions namely

natural drying

hydrostatic immersion

and hydrodynamic scouring

were considered. Combining with laboratory test results

digital image correlation techniques

scanning electron microscopy

and fractal theory

the influences of different water environments on the mechanical properties of rocks were systematically explored in terms of macro-mechanical parameters

distribution characteristics of strain fields

and microstructure. The results indicate that the softening coefficients of compressive strength and elastic modulus of hydrodynamically scoured specimens decrease by 0.07 and 0.06 units

respectively

compared to those of water-saturated specimens. The inflection point of the strain field differentiation rate-axial strain curve appears before the peak stress

associated with the localization of the fracture process zone

serving as a precursor signal for rock fracture. Compared to the effect of hydrostatic immersion

the precursor point of hydrodynamically scoured specimens appears earlier

as hydrodynamic scouring aggravates the development of internal defects

thereby facilitating the earlier appearance of the precursor point. Furthermore

the loss of mineral particles and cementing materials within the sandstone increases significantly after hydrodynamically scouring

leading to a more pronounced degradation of its microstructure than that of water-saturated specimens. This change is confirmed by the fractal dimension calculations of scanning electron microscope images

indicating that the hydrodynamically scoured specimens exhibit the largest fractal dimension.