Y. Fujii
Rock Mechanics Laboratory, Hokkaido
University
Many rock slope failures occurred recently in Hokkaido, Japan. It
is considered that sub-critical and critical crack growth near
rock surface played an important roll in the slope failures. Crack
behavior near rock surface is being investigated in order to
clarify the mechanisms of the slope failures in detail. Loading
rate-dependency of fracture toughness by using CB and the double
torsion tests is being carried out. Uniaxial compression tests of
rock or mortar specimens that simulate a steep cliff or have a
slit or an initial crack are also being carried out in order to
observe the effect of free surface on the crack growth. Results of
those tests are being used to improve a software, which is based
on Displacement Discontinuity Method, to simulate sub-critical and
critical crack growth near rock surface. Examples of crack growth
near rock surface can also be observed as burst like-rock failures
in quarries and sheeting joints in V-shaped valleys. Effects of
such environment as water content, pH, temperature, etc. on crack
growth are also being investigated for those geotechnical
applications.
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Example of displacement rate-dependency of fracture toughness for Shikotsu welded tuff. |
Example of crack growth from a notch in a compression test of rock block made of Shikotsu welded tuff. |
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Example of simulated crack propagation for a compression tests of a rock block based on Sih's theory and the author's theory. |
