MRI: Acquisition of Fiber Optic & Tiltmeter Systems for Measuring Deformations in Deep Underground Facilities

Montana Technological University, Butte MT

Investigators

Abstract

This award will provide funding to acquire state-of-the-art fiber optic and tiltmeter sensor systems for monitoring deformations in deep underground facilities, such as tunnels, mines, and laboratories. The research facilitated by this acquisition will entail utilization of existing fiber optic technology, but in a relatively novel application and at a site (the proposed DUSEL site located at the former Homestake Mine in Lead, SD) that would provide exciting potential for building long-term research synergy. Fiber optic instruments have previously been used in other engineering applications, but this will be the first comprehensive study of their performance in the challenging underground environment of large excavations in rock. Measurements of rock deformation will be made and compared in different spatial and temporal scales, at sites with drastically different expected behavior. The distributed and localized strain measurements at the DUSEL site will provide a crucial infrastructure database for several geomechanics, hydrology, and geoengineering experiments. The large volume of coverage makes it ideal for calibrating a mine-scale finite element model of deformation; as such, the fiber-optic strain experiment will contribute to design and construction of large rooms and to mine safety. Specifically, the fiber optic network will contribute to: (1) understanding how rock masses deform as a function of spatial scale over long times, (2) interpreting mine seismicity experiments, (3) testing of the coupling between fracture flow and deformation, and (4) safety as it provides a large-volume indication of the mine ?breathing? and can be deployed with a common measurement protocol for cavern monitoring. While there is a focus on deploying the fiber optic instrumentation in the Homestake site as part of the DUSEL initiative, other sites will serve to develop deployment and interpretation techniques and as locations for comparative studies. These include a) Fermilab in Illinois, where a tiltmeter-based monitoring system is already in place and has produced a 2-year database of observations, and b) actively-deforming mines, both coal and hardrock, to allow evaluation of the performance of the monitoring systems in less than ideal working conditions, in which the rock is expected to undergo substantial movement. A comprehensive comparative study such as this will lead to much wider use of this technology in the mining and tunneling industries. Research focused on providing a safe working environment in the subsurface has been central to Montana Tech for its entire century of existence. The new equipment will allow Montana Tech to make substantial new contributions in this area, benefiting operation of subsurface facilities and those who work there. Acquisition of these monitoring systems will also provide an unprecedented and very exciting opportunity for Montana Tech faculty to collaborate with high level researchers from the premiere doctoral institutions in the U.S. DUSEL is an exceptional opportunity for university, industry, and national laboratory researchers to work in partnership on problems from construction to basic geoscience and geo-engineering by occupying a single in situ, large-volume, underground laboratory with three-dimensional access. K-12 through graduate students and the public will gain an appreciation of how knowledge about underground rock mass response is gained by observing researchers pose questions, conduct experiments, make observations, and analyze and interpret the results. Montana Tech has very strong Undergraduate Research Program, and the opportunity to conduct research at the DUSEL is expected to be particularly attractive to student researchers. The PI has demonstrated great success involving female students and undergraduates in her research.