ボアホール周壁の破壊に関する破壊力学的研究 (第1報)

一軸圧縮試験

抄録

The fracture crack initiation around a small circular hole in the rectangular plate of rock specimen is observed as a model of borehole and circular cross-sectional roadway under the uniaxial compression.
In this experiment, the following unexpected phenomena are observed:
(1) the first fracture crack around the borehole is observed frequently in the region of compressive stress concentration;
(2) the tensile fracture crack initiated at the top and bottom wall of borehole propagates up to some limited length, to be arrested;
(3) the external stress (load) for the fracture crack initiation is dependent on the diameter of borehole;
(4) the external stress for the fracture crack initiation is much greater than that expected from the elasticity of isotropic homegeneous body.
All of these phenomena are not explained by conventional theories. However, applying the theory and concept of the linear fracture mechanics, all of these phenomena are explained as results of the interaction between the circular hole and pre-existing Griffith crack.