Abstract:

To investigate the damage-aging characteristics of sandstone under the action of acidic solution, experiments are conducted on the sandstone in the karst section of the Gaoligongshan tunnel. The transformation effects of acidic solution on the macroscopic morphology, defect morphology, pore structure, mineral composition, and porosity of sandstone are analyzed via scanning electron microscopy and X-ray diffraction experiments. The mass, size, and triaxial compressive strength of sandstone specimens in different solutions are measured at different immersion time nodes. The test results indicate the following: (1) The lower the solution pH, the greater the relative changes in porosity, mass, and size of the specimen; the change rate  is rapid in the initial stage of each solution and exhibits a stable trend in the later stage. (2) Under a confining pressure of 20 MPa, compared with the rock sample in the solution of pH=7 for 49 days, the triaxial peak compressive strength of the specimen in the solution of pH=1 is reduced by 20.98%, and the decrease rate declines with time. The cohesion and internal friction angle decrease with time, and the sensitivity of cohesion to the acidic solution is higher than that of the internal friction angle. (3) Under the erosion of acidic solution, the large consumption of feldspar and calcite and other components in the specimen changes the microstructure of the specimen. With a decrease in the pH of the solution, the specimen pore spacing increases, the cement consumption increases, and the corrosion holes and microcracks develop well.

Key words: acid solution, sandstone, chemical erosion, damage; aging characteristics, triaxial compression test, microstructure