Optical Fiber System for Measuring Pore Pressures during Progressive Failure

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Over the past 30 years, the use of fiber-optic sensing technology has spread across a broad range of scientific disciplines. The technology and its application within specialized instrumentation started to emerge in the 1980s with the advent of practical fiber-optics developed for the telecommunications industry. Advances in sensor size, performance, durability and reduced costs for passive optical fiber devices and active opto-electronic components has led to firmer penetration of fiber-optic sensor use in various industries. Within the geotechnical field, fiber optics are being increasingly used in laboratory and field applications where researchers must acquire high quality performance data within larger soil masses, along fractures or at the microscale within pore spaces. An experienced team of researchers in the Civil and Environmental Department in the Faculty of Engineering at the University of Alberta is proposing to integrate microfibre-optic pressure sensor technology used within the medical industry into several geotechnical studies. Having been originally developed for medical applications, these sensors allow for pressure drop measurements to be made within small sections of coronary arteries; the highly sensitive sensors produce consistent and accurate data superior to what was earlier possible. Our team's requested microfiber-optic system includes pressure sensors, a specialized data acquisition system and a modified shear box to enhance our existing servo-control direct shear device. This system will be utilized to capture internal pore pressure measurements of soil and rock during both shear and multiphase flow testing. Applying this technology to examine internal pore pressures is a unique opportunity to advance our understanding of coupled geomechanics occurring in soil and rock across a broad range of disciplines within geotechnical engineering and would be the first application of its kind in Canada. The requested microfiber-optic pore pressure monitoring system and modified shear box will enable our group to develop innovative approaches to monitor internal pore pressure responses and provide cutting edge research and training opportunities for students and researchers with strong skills in geotechnical engineering. These measurements will facilitate a greater understanding of the coupled geomechanics of soil and rock, which then allow engineers to optimize operations in a variety of confined underground sites (e.g. nuclear waste repositories, extraction of hydrocarbons from reservoirs).