Dr. Qi Zhao
Rotary shear experiments were conducted using a rock physics experimental apparatus that was paired with X-ray micro-computed tomography (µCT). This combination of technologies has significant advantages over conventional rotary shear experiments since it allowed for the direct observation of how two rough surfaces interact and deform at microscopic scale, without perturbing the experimental conditions. Intriguing observations were made pertaining to key areas of the study of fault evolution. The real contact area accounted for only less than 20% of the nominal area, and the number of real contact patches and their sizes showed positive correlations with the normal stress. Moreover, contact patch size distributions followed power law relations. Secondary off-fault fractures created by interlocking and breakdown of large contact patches were closely related to the sudden drops of frictional resistance, suggesting the dominant role of surface roughness on shear behavior especially at low stress.
Dr. Zhao received his PhD in Engineering (Geotechnical engineering and geophysics) at the University of Toronto. He is currently a Postdoctoral Fellow at the University of California, Berkeley.