Laboratory study for fracture toughness of rocks under sub-zero temperature conditions

Rock excavation for roads and tunnel portals is increasing in hilly regions of India where temperature drops below 0 degrees C. For excavation in rocks subjected to low temperature, a thorough knowledge of fracture toughness of the rock under sub-zero temperature condition is helpful for better excavation results. There is a growing interest in the study of fracture toughness of rocks, but less work has been done under sub-zero temperature conditions. A few rocks viz. Sandstone (fine grained), limestone, dolerite, agglomerate, basalt, dolomite, quartz- mica schist and calcium-biotite schist were tested to determine their fracture roughness under sub-zero temperatures. The study indicates that for practical purposes, fracture toughness increases with decrease in temperature (in the range from -10 degrees C to -50 degrees C) in case of all the above said rock masses.