Real-time CT testing of meso-damage evolution law of frozen cracked sandstone under uniaxial compression conditions

摘要

The CT real-time testing experiment have been done by applying the advanced CT techniques.The authors studied meso-damage mechanism of frozen sandstone test sample with two manmade prefabricated cracks under uniaxial compression conditions, and succeeded in getting CT images and CT values of frozen sandstone in various stages of damage from crack initiation and development to macroscopic crack formation and rock breaking. The results show that: so far as soft fractured sandstone with high water content is concerned,its strength will be improved considerably after it is frozen under negative temperature. Evolution of damage is of localized property and it is a non-linear real-times process. It is analogous to integral rock test sample that the course of frozen fractured sandstone from damage to destroy completely under the load of uniaxial compression can be divided into four stages: stage of linear development; stage of microscopic crack initiation and development; stage of rapid development of damage; and stage of accelerated development after reaching its peak. Damage evolution velocity of fractured rock at the four stages under the load of uniaxial compression is far quicker than intact rock. Split of new microcrack of frozen fractured rock and formation of final failure plane are closely related to the position and angle of existing prefabricated crack. The existence and geometric properties of prefabricated crack has important effects on dilatancy of fracture rock.