Pore characteristics and permeability changes of high-temperature limestone after rapid cooling by dry ice

This article adopts the fire extinguishing of tunnels as the engineering background, considers limestone as the research object, uses dry ice to quickly cool the limestone after high-temperature treatment at different temperatures (25–700 °C), and applies the microscopic magnifying glass, nuclear magnetic resonance, and permeability tester for studying the surface characteristics, porosity, and permeability of limestones. The research reports the following characteristics. (1) The color of the sample surface becomes lighter and whiter with an increase in the heating temperature. When the temperature above 400℃, the cracks appear on the surface of the rock and the micropores (0 ms < T2 < 10 ms), the number of mesopores (10 ms < T2 < 100 ms) began to develop. (2) The permeability of limestone increases with the increase of heat treatment temperature. When the heat treatment temperature above 400℃, the roughness of the rock surface becomes larger, and the permeability of the sample increases sharply. (3) The rapid cooling of dry ice aggravates the thermal damage effect of limestone, when the heating temperature above 400 °C, the porosity and permeability of limestone increase greatly, and the damage becomes more severe at 600 °C. Compared with natural cooling, dry ice cooling increases the permeability of limestone more significantly.