Abstract
This paper presents usefullness of the tension-softening model for an evaluation of Mode I fracture toughness in rocks. Rock fracture behavior is dominated by a fracture process zone. The fracture process zone in rock can be classfied into two types, such as planar fracture process zone and diffused microcrack zone. In this paper, the fracture process zone type for various rocks is examined based on microscopic strength distribution. The microscopic strength distribution is estimated from uniaxial tension test data using a statistical model of microcracking prior to damage localization. This examination demonstrates that the fracture process zone should be planar type in various rocks. Next, the fracture toughness of Iidate granite is evaluated using the tension-softening model. The fracture toughness value is compared with toughness values evaluated by means of other methods. The comparison results indicates that the tension-softening model can be utilized in a wide range of fracture ploblems in rock.
