“Cold Region Applications for MEMS-based In-place Inclinometers: Four Evaluation Case Studies”

摘要

Inclinometer probes are an industry standard to measure ground movement; however, this technology has drawbacks, including costly trips for manual measurements, operator error, and limited measurements due to casing deformation. Relatively new MEMS-based in-place inclinometers (M-IPIs) consist of MEMS accelerometer segments separated variously by flexible joints or field-connection systems, and encased in a watertight housing. M-IPIs provide nearly continuous ground movement measurements, accommodate greater ground movement due to their flexibility, and may contain temperature sensors, useful for frozen ground applications. Two M-IPIs from different manufacturers were evaluated at four research sites within Alaska: 1) to monitor creep in frozen ground (vertical installation); 2) to identify and monitor a slide shear zone (vertical installation); 3) to monitor thaw settlement under a newly-constructed embankment (horizontal installation); and 4) to identify movement mechanisms within a slide and to evaluate the M-IPI’s functionality through large amounts of shear. Each M-IPI was evaluated for ease of installation and subsequent retrieval, durability, and functionality in frozen ground. Measurements from both devices compared well to those from the inclinometer probe, indicating that these devices are suitable for use in cold regions. Field experience indicates that the installation procedure for each instrument is better undertaken at above freezing temperatures, however, due to required manual dexterity. For horizontal installations over permafrost, we recommend securing casing ends to posts anchored below the permafrost table, and we recommend replacing any cold-affected plastic components between installations to avoid unwanted breakage during re-installation.