Experimental study on the dynamic fracture mechanical properties of limestone after chemical corrosion

A rock mass structure has the risk of being subjected to both chemical corrosion and impact loading, which significantly affects the stability of the rock mass structure. In this study, the influence of corrosion on the dynamic fracture toughness of limestone was studied. NaCl and KHSO4 mixed solutions with different pH values (pH = 2, 4, and 6) were used to corrode nicked semicircle bending (NSCB) specimans in three groups and then tested with a split Hopkinson pressure bar (SHPB) device. Before performing the dynamic fracture tests, the porosity of the corroded specimens were obtained using the Nuclear magnetic resonance (NMR) system, and the damage variables were applied to describe the corrosion damage of the limestone. In addition, a high-speed camera, the JR 3D scanning system, scanning electron microscope (SEM) and X-ray fluorescence (XRF) technology were also carried out to examine the fractal dimensions, fracture roughness, micro-fracture morphology, and mineral composition and content. With the increase in the damage variable, the dynamic fracture toughness and fracture energy gradually decrease, while the fractal dimension of the fracture increases. The standard deviation of the 3D spatial distribution parameters, including the asperity height, slope angle, and aspect direction of the fracture surface mesh element planes, all increase, indicating a gradual increase in the fracture surface roughness due to the defects of the corrosion damage. The SEM and XRF results show that the chemical actions had a significant impact on the microstructure and mineral elements of the limestone. Finally, the relationship between the macroscopic mechanical parameters of the limestone specimens and the mechanism of the chemical corrosion damage was discussed.