X-ray computed tomography characterization of soil and rock mixture under cyclic triaxial testing: the effects of confining pressure on meso-structural changes
2019
Wang, Y. | Zhang, D. | Hu, Y. Z.
The mechanical meso-damage mechanism of soil and rock mixture (SRM) subjected to cyclic loading is very significant to evaluate the stability of construction and building structures composed of SRM. However, to date, few experiments have been done to investigate the physical mesoscopic damage evolution in SRM. In this work, cyclic triaxial tests were conducted on soil and rock mixture samples with rock block percentage of 40%, under confining pressures (CPs) of 60 kPa, 120 kPa, and 200 kPa using in situ X-ray computed tomography technique. The effects of confining pressure on the meso-structural changes have been visualized and investigated by CT image analysis. For the SRM samples, hysteresis loop on the cyclic stress–strain curves presents different pattern that is caused by the differential applied CP. The hysteresis loop area first decreased and then increased with plastic deformation increasing for samples under a CP of 60 kPa and 120 kPa; however, it shows monotonously decreasing trend under a CP of 200 kPa. In addition, after extracting cracks from the original CT images, it shows that the damage initiation moment of SRM is different even though with the same stress amplitude. The crack geometric parameters, however, decreased under larger confining pressure mainly due to the restriction of rock block movement. The stress dilatancy characteristics of SRM under various CPs also presented different trend from the volumetric change analysis on the CT images. The interlocking among rock blocks restricts the development of localized bands under high CP, and the ability to resist cyclic damage improves with the increase of CP.
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