Mechanics and Stability of the Lookout Creek Earth Flow

Abstract

Research Article| May 01, 1987 Mechanics and Stability of the Lookout Creek Earth Flow MARVIN R. PYLES; MARVIN R. PYLES Assistant Professor Department of Forest Engineering, Oregon State University, Corvallis, OR 97331 Search for other works by this author on: GSW Google Scholar KEITH MILLS; KEITH MILLS Geotechnical Specialist Oregon State Department of Forestry, 2600 State Street, Salem, OR 97310 Search for other works by this author on: GSW Google Scholar GEORGE SAUNDERS GEORGE SAUNDERS Research Assistant Department of Forest Engineering, Oregon State University, Corvallis, OR 97331 Search for other works by this author on: GSW Google Scholar Author and Article Information MARVIN R. PYLES Assistant Professor Department of Forest Engineering, Oregon State University, Corvallis, OR 97331 KEITH MILLS Geotechnical Specialist Oregon State Department of Forestry, 2600 State Street, Salem, OR 97310 GEORGE SAUNDERS Research Assistant Department of Forest Engineering, Oregon State University, Corvallis, OR 97331 Publisher: Association of Environmental & Engineering Geologists First Online: 02 Mar 2017 Online Issn: 1558-9161 Print Issn: 1078-7275 © 1987 Association of Engineering Geologists Environmental & Engineering Geoscience (1987) xxiv (2): 267–280. https://doi.org/10.2113/gseegeosci.xxiv.2.267 Article history First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation MARVIN R. PYLES, KEITH MILLS, GEORGE SAUNDERS; Mechanics and Stability of the Lookout Creek Earth Flow. Environmental & Engineering Geoscience 1987;; xxiv (2): 267–280. doi: https://doi.org/10.2113/gseegeosci.xxiv.2.267 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEnvironmental & Engineering Geoscience Search Advanced Search Abstract The Lookout Creek earth flow in the western Cascade Mountains of Oregon has moved an average of about 3.5 in. (8.9 cm) annually over the past decade. The currently active slide mass which has been moving for at least the past 80 years, overlies a 40,000-yr-old debris deposit. Monitored since 1975, measurable earth flow movement occurs only during the wet season; piezometric level, which is at or near the ground surface, varies only about 3 ft (0.9 m) between the wet and dry seasons. The base of the earth flow appears to be a shear zone about 10 in. (25 cm) thick located at a depth of 21.5 ft (6.5 m). Although earth flow movement does not correlate directly with piezometric levels, it does correlate with shear-zone pore-water pressures computed with a finite-difference approximation to the Terzaghi theory of one-dimensional consolidation; the finite-difference model uses piezometric pressure measured in the earth flow as a boundary condition. A rise in pore-water pressure in the shear zone of about 85 psf (4.1 kPa), or 1.4 ft (0.4 m) of water, is the calculated threshold value at which the earth flow begins to move. However, because the earth flow has a high drainage capacity, timber harvesting, which affects the ground-water regime, is unlikely to induce a large increase in movement. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.