Multi‑scale Experimental Investigations on the Deterioration Mechanism of Sandstone after high-temperature treatment

Abstract

Abstract With the continuous construction and development of deep engineering, in order to study the macro-damage and micro-change of temperature on sandstone, this paper conducts a series of Uniaxial Compressive Strength (UCS) tests, Acoustic Emission (AE) monitoring and Nuclear Magnetic Resonance (NMR) experiments on white sandstone treated at 25℃, 100℃, 300℃, 500℃ and 700℃. The study shows that the peak stress of the white sandstone specimens decreases with increasing temperature, and the corresponding axial strain increases significantly. The decrease in uniaxial compressive strength and modulus of elasticity increased sharply. The brittle-ductile transition occurs at about occurs between 500°C ~ 700°C. At temperatures between 25°C and 500°C, the peak AE energy occurs near the peak strength of the sandstone. The ringing counts of the sandstone specimens reached a maximum after the peak stress when the temperature was 700°C, and the peak AE energy gradually decreased at higher heating temperatures. The T2 spectrum curve and pore size curve of the white sandstone increased and gradually shifted to the right with the increase of the treatment temperature, and the total area of the T2 spectrum and porosity also gradually increased. There is a negative correlation between porosity and total area of T2 spectrum and peak stress and elastic modulus of white sandstone under high temperature. The micropores showed a monotonically decreasing trend with increasing temperature, the mesopores showed a trend of decreasing, then increasing, and finally decreasing, and the macropores-cracks enlarged the most.