ARMA UToronto Student Chapter Online Talk: Dr. Qi Zhao, Dr. Tianyang Guo

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Seminar by Dr. Qi Zhao and Dr. Tianyang Guo from Hong Kong Polytechnic University

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Title: Influence of proppant on the shear behavior of rough rock joints

Short Bio: Dr. Qi Zhao

Dr. Qi Zhao obtained his Ph.D. degree at the University of Toronto and then worked as a postdoctoral researcher at the University of Toronto and UC Berkeley. He joined the Hong Kong Polytechnic University in June 2020 as an assistant professor at the Department of Civil and Environmental Engineering. His research interests cover several aspects across rock mechanics and geophysics, including in situ rock physics experiments under X-ray micro-CT, laboratory earthquakes, and rock joint surface roughness and shear behavior.

Short Abstract

Shear stimulation aided by proppant emplacement has been proven to be a useful approach to improve the hydraulic permeability of fractured hydrocarbon and geothermal reservoirs. The shear behavior of rock joints plays a dominant role in the effectiveness and safety of shear stimulations. In this presentation, I will present our recent work on shear behavior of propped rock joints under different normal stress and proppant conditions. Our results show that proppant lower and flatten the failure envelope, making the joints more susceptible to shear failure. Proppant also significantly alter the shear stress-displacement curves and reduce the shear dilation. Our study suggests that the shear behavior of a propped joint is controlled by a combined effect of proppant conditions, normal stress, and surface roughness. Understanding the interplay of these factors is the key to improve the efficiency of geo-energy extraction and prevent induced seismicity.

Title: Understanding the microcracking behavior of granite from acoustic emission and microscopic observation

Short Bio: Dr. Tianyang Guo

Dr. Tianyang Guo earned his Ph.D. degree in the field of rock mechanics at the University of Hong Kong in 2020 with Dr. Louis Wong. He has been doing postdoctoral research with Dr. Qi Zhao at the Hong Kong Polytechnic University since 2021. His research interests are acoustic emission data mining, microstructural analysis, microcracking mechanisms of granite.

Short Abstract

Rock cracks at various scales (e.g., crystal planes, microcracks, cleavages, fissures, joints, beddings, and faults) control a number of Earth’s dynamic processes as well as the efficiency and safety of geotechnical engineering practices. A thorough study of the microcracking behavior of rocks leads to a better understanding and prediction of the associated macroscopic cracking process. Although the characteristics of the fracture process zones (FPZs) caused by microcracking in granite under static mode I loading have been extensively investigated experimentally, the microcracking mechanisms of granites with different mineralogy and textural property are still not clearly understood and merit further study. To advance the understanding of the microcracking mechanisms, this study aims to experimentally study the effects of the mineralogy and textural property of granites on their microcracking behavior. Based on the semi-circular bending test, the microcracking mechanisms of Hong Kong granites are investigated using acoustic emission and microscopic observation techniques. Based on the results, an extended conceptual model which accounts for the effects of pre-existing microcracks is proposed to better describe the FPZ evolution prior to unstable crack propagation in crystalline rocks.

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Organizer ARMA UToronto Student Chapter

Organizer of ARMA UToronto Student Chapter Online Talk: Dr. Qi Zhao, Dr. Tianyang Guo

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