Parks/Chena Ridge Air Convection Embankment Performance Report

摘要

This report describes the thermal performance of an experimental Air Convention211u001eEmbankment (ACE) that was included as an experimental feature in the Parks/Chena 211u001eRidge Interchange project (Federal Project No. I-0A4-5(7), State of Alaska 211u001eProject No. 63538). Data is included for October 1998 through September 1999. 211u001eAdditional reports by the same author (cited in this report) describe the design 211u001ethe design and construction of the ACE experimental feature, and data analyses 211u001ethat cover the period from November, 1996 through September, 1998. ACE is 211u001ecomposed of coarse, open-graded fill material that promotes circulation of air 211u001ethroughout the embankment mass during winter, thus cooling and preserving 211u001eunderlying permafrost foundation soils. Natural wintertime temperature gradients 211u001eare established within the extremely porous ACE, and produce unstable conditions 211u001ethroughout the enclosed air mass. These instabilities initiate and sustain 211u001econvective air cells that remove heat from underlying foundation soils, and eject 211u001eheat at the cold embankment surface. The summertime temperature gradient within 211u001ethe embankment produces stable conditions, so air circulation ceases within the 211u001eembankment. The overall effect is that the entire embankment becomes a passive, 1-211u001eway heat valve, i.e., a refrigeration system that helps protect ice-rich 211u001efoundation materials from thaw and loss of strength. Results to date indicate 211u001ethat the system is performing successfully.