Experimental Investigations on Pore Structure and Mechanical Properties of Sandstone Subjected to Chemical Corrosion

Rock materials used as building stone and construction materials are usually subjected to the corrosion of hydro-chemical solutions. To investigate the effect of chemical corrosion on the change of pore structure and mechanical properties of sandstones, the nuclear magnetic resonance (NMR) technique was used for the measurement of porosity and $T_{2}$ spectrum distribution. Series of triaxial compression tests with the confining pressure of 0, 5, 10, and 20 MPa were then conducted for rock specimens treated with chemical corrosions. The test results revealed that, compared with the rock specimens in their natural state, after chemical corrosion the porosity increased, the $T_{2}$ spectrum distribution was broadened successively, and the pore structure became more complex with the fractal dimension increasing. The proportions of pores with different sizes were various with the change of chemical solutions and the immersion time. Moreover, under a certain confining pressure, the peak strength, elastic modulus, internal friction angle, and cohesion of sandstone after chemical corrosions decreased, but the corresponding peak strain increased. A chemical damage variable was proposed based on the porosity of sandstone and the order of effect of chemical solutions on pore structure and mechanical properties of sandstone was obtained as H2SO4 solution > NaOH solution > distilled water. Finally, a decay model considering both of chemical damage and confining pressure was established to predict the triaxial compressive strength of sandstone treated with chemical corrosion.