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Abstract Thermal cracking of rock is a very common natural phenomenon in engineering. The experiments on acoustic emission(AE) characteristics and permeability evolution of sandstone and granite were carried out at temperature ranging from room temperature(RT) to 600 ℃ by using 600 ℃ 20 MN servo-controlled rock triaxial testing machine with high temperature and high pressure (HTHP);and it reveals the related features between thermal cracking law and induced permeability. The results show as follows:(1) There exists a thermal-cracking threshold value in the heating process from RT to 600 ℃ as a result of thermal effect. According to AE characteristics induced by rock thermal cracking,the cracking threshold temperature of granite from Pingyi,Shandong Province in China is 65 ℃ and the one of fine-grained sandstone from Yongcheng,Henan Province in China is 170 ℃,respectively. (2) The behavior of rock thermal cracking is discontinuity and multi-period from RT to 600 ℃ with temperature rising over the threshold temperature. It neither increases nor reduces monotonously in the heating process;and there exist more than two peak value areas. (3) The rock permeability appears multi-peak value area because of the multi-period of thermal cracking with temperature increasing. The relative lowering permeability lag occurs after the quietude of AE in the peak value area of permeability. But the permeability remains in a high level and it is more and more high with the increasing happening times of AE drastic period.
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Received: 01 April 2010
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