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Abstract For knowing the variation characteristic of rock microstructure under freezing and thawing cycles，the experimental study on granite sample is conducted under different freezing and thawing cycles of 0 time，10，20，30 and 40 times with the freezing temperature of －40 ℃ and thawing temperature of 20 ℃. The nuclear magnetic resonance(NMR) is used to test the samples after freezing and thawing cycles；and the crosswise relaxation time T2 distribution and NMR imaging are obtained. The results show that：T2 distribution of granite exhibits three peaks and the subtotal spectrum area between the first peak and second peak occupies more than 98% of the total area，which means the micro pores are in the majority. After different freezing-thawing cycles of 10，20，30 and 40 times，the T2 spectrum area has changed obviously；and the porosity has increased by 14%，0.9%，16.2% and 1.6% respectively. Also，the space distributions of pores have been visually shown by the NMR imaging. The variation law of NMR characteristics in rock under freezing-thawing cycles has provided the reliable experimental results for the research works of rock damage mechanism under freezing and thawing cycles.
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Received: 09 October 2011
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2012, Vol. 31 
