Evaluation of Fracture Toughness of Rocks in Wet and Chemical Condition

Abstract

Three point bending tests were conducted to investigate the effect of the chemical and wet environments on the fracture toughness of Inada granite, Kimachi sandstone, and Shin-Komatsu andesite. The new testing method was also suggested here so that the chemical solution or water constantly can exist at the crack tip during the tests. The fracture toughness was evaluated by both ISRM suggested method and AE (Acoustic Emission) technique. In AE technique AE hypocenter distribution was determined to pinpoint the crack front and process zone, then stress intensity factor was calculated using the crack length evaluated by AE hypocenters distribution. Fracture toughness of the granite, in which significant decrease has not been reported before even in wet condition, dropped 25 % in wet condition when compared to the one in dry condition, and also 37 % down in Kimachi sandstone. In Shin-Komatsu andesite, fracture toughness in wet or chemical condition dropped about 10 % from dry condition. It was found that the form of crack, estimated by AE hypocenters, have two patterns in Inada Granite. But in other rocks, there are only one pattern infracture loading. The AE behaviors in wet condition implies that the fracture mechanism could be changed from brittle manner to possibly ductile one.