X-ray computed tomography technique to observe shear banding in dense sands

For more than a decade, X-ray computed tomography (CT) scanners have been available for industrial nondestructive evaluation. One of the applications in the field of geotechnical engineering is that shear zones developed in dense sand can be clearly identified as dilated areas of lower attenuation properties compared to the surrounding areas. Since 1991, this inspection technique have been utilized at CRIEPI in order to investigate complicated failure mechanisms of model ground under various boundary conditions. In the first half of this paper, a typical example of physical model studies is presented to demonstrate effective use of X-ray CT scanners; the study of cavity expansion in dense sand modeling pressuremeter tests. In the second half, the results of investigation into the accuracy of this X-ray CT are reported in respect of identifying locations of shear zones and measuring their lengths.