刃先接触面における岩石の降伏応力

岩石の切削における破壊の機構

抄録

As the results of microscopic observations on the failure planes produced in rock cutting, it was ascertained that there were two processes in i k failure. The first is the process of shear fractures caused directly along with the advance of blade. 2 second. is the process of an extension fracture due to the crack propagation which is brought about after the development of the yielding region under the high confining pressure.
In the present paper, yielding stresses of rock are analyzed with regard to the rake face and backing-off face of the blade in each process above mentioned. The analysis is done as a problem of a plane strain and an incipient plasticity of yielding region whose configuration is presumed on the basis of experimental evidence. The rock is assumed to yield when the Mohr stress circle becomes tangent to a parabolic failure envelope and the blade is represented by a two-dimensional idealized wedge. At the blade-rock interface the stress field no only satisfies the yield condition but also is such that the ratio of the shearing stress to the normd stress is qual to the coefficient of friction.
The analysis provides good agreement with the experimental results on the yielding stresses if the “size effectr” of compressive strength of rock is taken into consideration. Therefore, it may be possible to estimate the yielding stresses at blade-rock interface in rock cutting with considerable accuracy by applying theanalytical method in this paper.