|Budget Amount *help
¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2003: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2002: ¥500,000 (Direct Cost: ¥500,000)
We have proposed a method to estimate the size effect on shear properties of rock fracture using JRC-diagram newly developed by us to estimate the surface roughness of a rock fracture rationally based on a fractal model. In order to confirm the validity of this our method for the JRC evaluation, simple shear testing equipment which consisted of precise syringe pump, hydraulic piston cell, rigid frame and shear box was newly designed and was set up, and shear test was carried out by using it. The specimens for the shear test were prepared artificially by the following way. First, numerical topography data of a fracture surface were created using Brown's method. ' Second, a fracture surface was carved on a modeling wax using a NC modeling machine and a matrix of silicon rubber was made. Finally, fracture specimen of mortal was made by molding. By this way, we succeeded in setting the interlocking asperity size, surface roughness, and material strength at will to any specimen. Three types of the specimen whose interlocking asperity size is 2mm, 4mm, and 6mm and whose size is 30mmx30mm, 60mmx60mm, and 90mmx90mm respectively were prepared. As a result of the shear tests for these specimens, the tendency in which the peak shear strength lowered with the increase in the interlocking asperity size was confirmed. For each specimen, JRC was evaluated by using JRC-diagram and the method presented by Barton et al., and they were compared to the JRC estimated from the experimental results. As the result, it was proven that JRC-diagram gives more correct JRC than Barton's. method. In addition, it was proven from the result of shear test for the specimens of sandstone and granite that JRC-diagram could give correct JRC, if the interlocking asperity size is correctly evaluated.