Microfracturing Processes of Rock by Real-Time Observation of X-ray CT
Wu Yanqing(1,2),Cao Guangzhu(1,3),Wang Dianwu(3)
(1 Xi'an University of Technology Xi'an 710048 China) (2 Shanghai Jiaotong Unive rsity Shanghai 200240 China
(3 Liaoning Provincial Bureau of Hydrology and Water Resource Investigation, Shen yang 110003 China)

Abstract: To understand the fundamental problems of earthquake occurrence in detail, the determination of microfracturing and propogating in inner rock is cons idered to be useful for real-time detecting. Two types of sandstones are scanned by multislice spiral CT (MSCT) with high resolution under uniaxial compressive condition. Acorreding to the treatment and analysis of CT images, it is found that the variances of the difference of CT images are concerned closely with the propagating rate of microfractures. The relation curves between this variances and stresses of sandstone samples indicate the threshold value of microfractures propagating in sandstone samples can be identified easily. For a soft sandstone, the initiation of microfractures is 55% of the peak strength of a sandstone samples, and the whole propagating strength of microfractures is about 73% of the peak strength of a sandstone sample. For the hardy sandstone, the initiation of microfractures is 64.5% of the peak strength, and the whole propagating strength of microfractures is about 79% of the peak strength of a sandstone sample. An d the propagating process of microfractures in the sandstones can be found intuitively. During the initial stage of compression, the propagating rate of microfractures increases very slowly with the enhanced compression. When the compressio n approaches to the threshold values of microfracturing initiation, the propagat ing rate of microfractures is decline rapidly. After the microfracturing initiation, the propagating rate of microfractures increases before the occurrence of m acrofractures.
Keywords: sandstone, uniaxial compressive condition, micro-fracture, threshold value of microfracture propagating, X-ray CT.