Shigen-to-sozai, Vol.118, No.9, pp.605-611.
Effect of Elevated Temperature on Fracture Toughness of Kimachi Sandstone
Takahiro FUNATSUa, Masahiro SETOb, Hideki SHIMADAc and Kikuo MATSUId
| a. Ph.D. student, Department of Earth Resources
and Mining Engineering, Graduate School of
Engineering, Kyushu University b. Senior Planning officer, Planning Headquarters, National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8567, Japan c. Associate Professor, Department of Earth Resources and Mining Engineering, Graduate School of Engineering, Kyushu University d. Professor, Department of Earth Resources and Mining Engineering, Graduate School of Engineering, Kyushu University |
| In order to understand the effect of elevated
temperature on fracture toughness, fracture
toughness experiments were carried out at
increasing temperatures from room temperature
to 20Gb using the single edge-notched round
bar in bending (SENRBB) specimen and the
semi-circular bend (SCB) specimen of Kimachi
sandstone. The paper firstly describes the
methodology for the evaluation of level I
fracture toughness and crack growth resistance
curve. Crack growth resistance curve is also
shown to consider the increase of the crack
growth resistance with crack growth. The
experimental results showed that fracture
toughness of Kimachi sandstone did not vary
significantly at temperature up to 125℃
and increased with elevated temperature beyond
125℃. The level I fracture toughness from
the SENRBB testing increased by approximately
40% at 200℃ when compared to the value at
room temperature. The variation of fracture
toughness can be explained in terms of thermally-induced
microcracks and dehydration of interlayer
water and adsorptive water included in clay
material such as montmorillonite. The thermally
induced microcracks, which were confirmed
under microscope, lower the fracture toughness
due to decrease in crack growth resistance,
while the dehydration of interlayer water
and adsorptive water in the rock specimen,
which were confirmed by measuring weight
under several temperatures, raises the fracture
toughness because of increase in bonding strength between the mineral particles. Based on the strain and Young's modulus measurements tinder elevated temperature, it was concluded that the dehydration of interlayer and adsorptive water and the thermally induced microcracks influenced on the fracture toughness of Kimachi sandstone. |
| KEY WORDS: Sandstone, Fracture Toughness, Elevated Temperature, Microcrack, Clay Material |