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Abstract Full-digital hydraulic pressure and high temperature fatigue testing system with scanning electron microscope(SEM) is used to real-time observe and study thermal cracking of Beishan granite under different temperatures. Experimental results indicate that the threshold temperatures of thermal cracking of Beishan granite is 68 ℃–88 ℃. At the lower temperatures，intergranular thermal cracking is the main thermal cracking for Beishan granite. However，at the higher temperatures，transgranular cracking and coupling of intergranular and transgranular thermal cracking are the main cracking for Beishan granite. Beishan granite thermal cracking is not only effected by thermal expansion mismatch and thermal expansion anisotropy of minerals，but also effected by the physico-mechanical and thermal properties of mineral grains and mineral particle shape structures. Fluid inclusions within the granite may also effect the thermal cracking of Beishan granite，which is a new effect mechanism for thermal cracking. At microscopic and mesoscopic levels，thermal cracking has been classified；and different mechanisms for intergranular and transgranular thermal crackings can be quantitatively interpreted using the fractal models. When the temperature rises above 250 ℃，there is thermal melting effect in Beishan granite，which leads to a decrease in thermal cracking amount. The relationship between temperature and its corresponding thermal cracking amount fits Gauss curve well.
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Received: 14 February 2011
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2011, Vol. 30 
