DOCSLIB.ORG

Mass Wasting Mass Wasting Mass Wasting

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Mass Wasting Mass Wasting Mass Wasting Mass Wasting Mass Wasting Mass Wasting Important triggering factors The downslope movement of rock, • Saturation regolith, and soil under the direct influence of gravity • Oversteepening • Removal of vegetation Gravity is the controlling force • Ground vibrations Important triggering factors Important triggering factors Important triggering factors Saturation of the material with water Oversteepened slopes Oversteepened slopes • Destroys particle cohesion • Unconsolidated granular particles assume • Undercutting by streams • Water adds weight a stable slope called the angle of repose • Undercutting by human interference • Stable slope angle is different for various • Addition of material to top of slope materials • Natural—deposition • Oversteepened slopes are unstable • Human-caused--construction Types of mass wasting Important triggering factors Mass Wasting processes Types of mass wasting processes • Removal of anchoring vegetation Defined by Defined by the material involved • Wildfires • The material involved • Debris • Drought • The movement of the material •Mud • Development, logging •Earth •Rock • Ground vibrations • from earthquakes 1 Types of mass wasting Types of mass wasting processes processes Forms of mass wasting •Slump Defined by the movement of the material Defined by the movement of the material • Rockslide The character of the movement The rate of the movement • Debris flow •Fall •Fast • Earth flow • Slide •Slow • Creep •Flow • Solifluction USGS Landslide Types of mass wasting Types Forms of mass wasting Slump • Rapid movement along a curved surface • Occur along oversteepened slopes • http://pubs.usgs.gov/fs/2004/3072/fs-2004-3072.html Slump—diagram Slump Government Hill, AK • 1964 • http://walrus.wr.usgs.gov/geotech/radaraapg/fig4.html • http://www.physicalgeography.net/fundamentals/10x.html 2 Government Hill, AK Forms of mass wasting Rockslide—diagram seismic cross section Rockslide • Rapid • Blocks of bedrock move down a slope Cousin to Rockfall • http://www.kmtr.com/mediacenter/[email protected],[email protected],4200@video. kmtr.com,[email protected],[email protected]&navCatId=5&2=2 • http://walrus.wr.usgs.gov/geotech/radaraapg/fig5.html Elkton, Oregon, March 4, 2006 Elkton, Oregon, March 4, 2006 Nevado Huascarán • Peru 1970 • Buried two towns • 18,000 killed • Geologists warned government of potential • http://www.kmtr.com/news/local/story.aspx?content_id=010798AE-AF2F-41D5-93F5-120A64493D45 • http://www.kmtr.com/news/local/story.aspx?content_id=010798AE-AF2F-41D5-93F5-120A64493D45 http://landslides.usgs.gov/html_files/landslides/slides/slide5.htm • http://www.goldengatephoto.com/WestUS/wyother.html#grosventre Gros Ventre rockslide--diagram Gros Ventre Slide Lake, Wyoming landslide—photo • http://www.uwsp.edu/geo/projects/geoweb/participants/dutch/VTrips/GrosVentre.HTM 3 Sherman Glacier Rock Rock Fall Rock Fall Avalanche, March 1964 • July 1996 • Yosemite • http://landslides.usgs.gov/html_files/landslides/slides/slide9.htm • http://sts.gsc.nrcan.gc.ca/geoscape/vancouver/graphics/mountain1.gif Snohomish County, WA Forms of mass wasting January 2006 Debris flow (mudflow) • Rapid flow of debris with water • Confined to channels • Dry areas with heavy rains • Lahar composed of volcanic materials • http://www.komotv.com/stories/41527.htm US 50, Sierra La Conchita, La Conchita, California Nevadas, California California 1997 • Spring 1995 • No one injured or killed • February 2005 • http://landslides.usgs.gov/html_files/landslides/slides/slide21.htm http://landslides.usgs.gov/monitoring/hwy50/index.php 4 La Conchita, 2005 Slide Mountain, Nevada, 1983 Debris flow damage http://landslides.usgs.gov/html_files/landslides/slides/slide2.htm • http://www.redcross.org/article/0,1072,0_312_3943,00.html Toutle River Debris Flow Nevado del Ruiz Lahar debris flow • http://landslides.usgs.gov/html_files/landslides/slides/slide13.htm • http://pubs.usgs.gov/fs/fs-176-97/fs-176-97.html • http://volcanoes.usgs.gov/Hazards/What/Lahars/RuizLahars.html Eruption of Nevado del Ruiz Confluence of lahars, Nevado del Ruiz Armero site, Nevado del Ruiz • http://volcanoes.usgs.gov/Hazards/What/Lahars/RuizLahars.html • http://volcanoes.usgs.gov/Hazards/What/Lahars/RuizLahars.html • http://volcanoes.usgs.gov/Hazards/What/Lahars/RuizLahars.html 5 Philippine Landslide, 2006 Scar of Philippine landslide Forms of mass wasting Earthflow • Rapid or slow • Typically occur on hillsides in humid regions • Water saturates the soil • Liquefaction: associated with earthquakes and clay soils • http://news.yahoo.com/news?tmpl=story&u=/060219/481/xbm10202190643 • http://www.alertnet.org/thenews/pictures/MAN52D.htm Earthflow—diagram Hollywood Hills, CA Niigata, Japan, 1964 • January 2005 • http://www.cnn.com/interactive/weather/0501/gallery.storms/frameset.exclude.html • http://www.ce.washington.edu/~liquefaction/selectpiclique/nigata64/tiltedbuilding.jpg Anchorage, AK 1964 liquefaction damage Alaska, 1964 1964 • http://www.owlnet.rice.edu/~sehh/AlaskaEQ/Alaska_Sci/EQScience • http://www.ce.washington.edu/~liquefaction/selectpiclique/alaska64/landslideintowater.jpg • http://walrus.wr.usgs.gov/geotech/radaraapg/fig5.html • Hyperlink to sand boil liquefaction http://walrus.wr.usgs.gov/geotech/images/TIsandboils.mov 6 Sheffield Dam, 1925 Forms of mass wasting Cause of creep—frost heave Santa Barbara Creep County • Slow movement of soil and regolith downhill Earth-quake • Causes fences and utility poles to tilt caused flow • http://www.ce.washington.edu/~liquefaction/selectpiclique/dams/sheffielddam1.jpg Some visible effects of creep Creep Creep • Bedrock curled • Curved due to creep trunks mass wasting due to soil creep • http://classes.colgate.edu/dkeller/geol101/massw/images/creep1.jpg • http://www.ngdc.noaa.gov/seg/hazard/slideset/6/6_140_slide.shtml Ground subsidence in Forms of mass wasting Solifluction Lobes Alaska due to solifluction Solifluction • Slow movement in areas underlain by permafrost • Upper (active) soil layer becomes saturated and slowly flows over a frozen surface below • http://piru.alexandria.ucsb.edu/collections/geography3b/misc/solifluction_lobes_jpg%5b1%5d.jpg 7 Mass Wasting Potential Mass Wasting Potential Measuring ground EXPLANATION LANDSLIDE INCIDENCE EXPLANATION Low (less than 1.5% of area involved) movement Moderate (1.5%-15% of area involved) LANDSLIDE INCIDENCE High (greater than 15% of area involved) Low (less than 1.5% of area involved) Moderate (1.5%-15% of area involved) LANDSLIDE SUSCEPTIBILITY/INCIDENCE Moderate susceptibility/low incidence High (greater than 15% of area involved) High susceptibility/low incidence High susceptibility/moderate incidence LANDSLIDE SUSCEPTIBILITY/INCIDENCE Moderate susceptibility/low incidence High susceptibility/low incidence High susceptibility/moderate incidence Mass Wasting The downslope movement of rock, regolith, and soil under the direct influence of gravity Gravity is the controlling force Important triggering factors • Saturation of the material with water • Oversteepening • Devegetation •Vibration 8.
Load more

Recommended publications
  • Short-Lived Increase in Erosion During the African Humid Period: Evidence from the Northern Kenya Rift ∗ Yannick Garcin A, , Taylor F
    Earth and Planetary Science Letters 459 (2017) 58–69 Contents lists available at ScienceDirect Earth and Planetary Science Letters www.elsevier.com/locate/epsl Short-lived increase in erosion during the African Humid Period: Evidence from the northern Kenya Rift ∗ Yannick Garcin a, , Taylor F. Schildgen a,b, Verónica Torres Acosta a, Daniel Melnick a,c, Julien Guillemoteau a, Jane Willenbring b,d, Manfred R. Strecker a a Institut für Erd- und Umweltwissenschaften, Universität Potsdam, Germany b Helmholtz-Zentrum Potsdam, Deutsches GeoForschungsZentrum GFZ, Telegrafenberg Potsdam, Germany c Instituto de Ciencias de la Tierra, Universidad Austral de Chile, Casilla 567, Valdivia, Chile d Scripps Institution of Oceanography – Earth Division, University of California, San Diego, La Jolla, USA a r t i c l e i n f o a b s t r a c t Article history: The African Humid Period (AHP) between ∼15 and 5.5 cal. kyr BP caused major environmental change Received 2 June 2016 in East Africa, including filling of the Suguta Valley in the northern Kenya Rift with an extensive Received in revised form 4 November 2016 (∼2150 km2), deep (∼300 m) lake. Interfingering fluvio-lacustrine deposits of the Baragoi paleo-delta Accepted 8 November 2016 provide insights into the lake-level history and how erosion rates changed during this time, as revealed Available online 30 November 2016 by delta-volume estimates and the concentration of cosmogenic 10Be in fluvial sand. Erosion rates derived Editor: A. Yin −1 10 from delta-volume estimates range from 0.019 to 0.03 mm yr . Be-derived paleo-erosion rates at −1 Keywords: ∼11.8 cal.
    [Show full text]
  • Deformation Characteristics of the Shear Zone and Movement of Block Stones in Soil–Rock Mixtures Based on Large-Sized Shear Test
    applied sciences Article Deformation Characteristics of the Shear Zone and Movement of Block Stones in Soil–Rock Mixtures Based on Large-Sized Shear Test Zhiqing Li 1,2,3,*, Feng Hu 1,2,3, Shengwen Qi 1,2,3, Ruilin Hu 1,2,3, Yingxin Zhou 4 and Yawei Bai 5 1 Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China; [email protected] (F.H.); [email protected] (S.Q.); [email protected] (R.H.) 2 College of Earth and Planetary Science, University of Chinese Academy of Sciences, Beijing 100049, China 3 Innovation Academy of Earth Science, Chinese Academy of Sciences, Beijing 100029, China 4 Yunnan Chuyao Expressway Construction Headquarters, Chuxiong 675000, China; [email protected] 5 Henan Yaoluanxi Expressway Construction Co. LTD, Luanchuan 471521, China; [email protected] * Correspondence: [email protected] or [email protected]; Tel.: +86-13671264387 Received: 27 July 2020; Accepted: 15 September 2020; Published: 17 September 2020 Abstract: Soil–rock mixtures (SRM) have the characteristics of distinct heterogeneity and an obvious structural effect, which make their physical and mechanical properties very complex. This study aimed to investigate the deformation properties and failure mode of the shear zone as well as the movement of block stones in SRM experimentally, not only considering SRM shear strength. The particle composition and proportion of specimens were based on field samples from an SRM slope along national highway 318 in Xigaze, Tibet. Shear zone deformation tests were carried out using an SRM-1000 large-sized geotechnical apparatus controlled by a motor servo, considering the effects of different stone contents by mass (0, 30%, 50%, 70%), vertical pressures (50, 100, 200, 300, and 400 kPa), and block stone sizes (9.5–19.0, 19.0–31.5, and 31.5–53.0 mm).
    [Show full text]
  • Slope Stability Back Analysis Using Rocscience Software
    Slope Stability Back Analysis using Rocscience Software A question we are frequently asked is, “Can Slide do back analysis?” The answer is YES, as we will discover in this article, which describes various methods of back analysis using Slide and other Rocscience software. In this article we will discuss the following topics: Back analysis of material strength using sensitivity or probabilistic analysis in Slide Back analysis of other parameters (e.g. groundwater conditions) Back analysis of support force for required factor of safety Manual and advanced back analysis Introduction When a slope has failed an analysis is usually carried out to determine the cause of failure. Given a known (or assumed) failure surface, some form of “back analysis” can be carried out in order to determine or estimate the material shear strength, pore pressure or other conditions at the time of failure. The back analyzed properties can be used to design remedial slope stability measures. Although the current version of Slide (version 6.0) does not have an explicit option for the back analysis of material properties, it is possible to carry out back analysis using the sensitivity or probabilistic analysis modules in Slide, as we will describe in this article. There are a variety of methods for carrying out back analysis: Manual trial and error to match input data with observed behaviour Sensitivity analysis for individual variables Probabilistic analysis for two correlated variables Advanced probabilistic methods for simultaneous analysis of multiple parameters We will discuss each of these various methods in the following sections. Note that back analysis does not necessarily imply that failure has occurred.
    [Show full text]
  • Beyond the Angle of Repose: a Review and Synthesis of Landslide Processes in Response to Rapid Uplift, Eel River, Northern Eel River, Northern California
    Portland State University PDXScholar Geology Faculty Publications and Presentations Geology 2-23-2015 Beyond the Angle of Repose: A Review and Synthesis of Landslide Processes in Response to Rapid Uplift, Eel River, Northern Eel River, Northern California Joshua J. Roering University of Oregon Benjamin H. Mackey University of Canterbury Alexander L. Handwerger University of Oregon Adam M. Booth Portland State University, [email protected] Follow this and additional works at: https://pdxscholar.library.pdx.edu/geology_fac David A. Schmidt Univ Persityart of of the W Geologyashington Commons , Geomorphology Commons, and the Geophysics and Seismology Commons Let us know how access to this document benefits ou.y See next page for additional authors Citation Details Roering, Joshua J., Mackey, Benjamin H., Handwerger, Alexander L., Booth, Adam M., Schmidt, David A., Bennett, Georgina L., Cerovski-Darriau, Corina, Beyond the angle of repose: A review and synthesis of landslide pro-cesses in response to rapid uplift, Eel River, Northern California, Geomorphology (2015), doi: 10.1016/j.geomorph.2015.02.013 This Post-Print is brought to you for free and open access. It has been accepted for inclusion in Geology Faculty Publications and Presentations by an authorized administrator of PDXScholar. Please contact us if we can make this document more accessible: [email protected]. Authors Joshua J. Roering, Benjamin H. Mackey, Alexander L. Handwerger, Adam M. Booth, David A. Schmidt, Georgina L. Bennett, and Corina Cerovski-Darriau This post-print is available at PDXScholar: https://pdxscholar.library.pdx.edu/geology_fac/75 ACCEPTED MANUSCRIPT Beyond the angle of repose: A review and synthesis of landslide processes in response to rapid uplift, Eel River, Northern California Joshua J.
    [Show full text]
  • Soil and Rock Properties
    Soil and rock properties W.A.C. Bennett Dam, BC Hydro 1 1) Basic testing methods 2) Soil properties and their estimation 3) Problem-oriented classification of soils 2 1 Consolidation Apparatus (“oedometer”) ELE catalogue 3 Oedometers ELE catalogue 4 2 Unconfined compression test on clay (undrained, uniaxial) ELE catalogue 5 Triaxial test on soil ELE catalogue 6 3 Direct shear (shear box) test on soil ELE catalogue 7 Field test: Standard Penetration Test (STP) ASTM D1586 Drop hammers: Standard “split spoon” “Old U.K.” “Doughnut” “Trip” sampler (open) 18” (30.5 cm long) ER=50 ER=45 ER=60 Test: 1) Place sampler to the bottom 2) Drive 18”, count blows for every 6” 3) Recover sample. “N” value = number of blows for the last 12” Corrections: ER N60 = N 1) Energy ratio: 60 Precautions: 2) Overburden depth 1) Clean hole 1.7N 2) Sampler below end Effective vertical of casing N1 = pressure (tons/ft2) 3) Cobbles 0.7 +σ v ' 8 4 Field test: Borehole vane (undrained shear strength) Procedure: 1) Place vane to the bottom 2) Insert into clay 3) Rotate, measure peak torque 4) Turn several times, measure remoulded torque 5) Calculate strength 1.0 Correction: 0.6 Bjerrum’s correction PEAK 0 20% P.I. 100% Precautions: Plasticity REMOULDED 1) Clean hole Index 2) Sampler below end of casing ASTM D2573 3) No rod friction 9 Soil properties relevant to slope stability: 1) “Drained” shear strength: - friction angle, true cohesion - curved strength envelope 2) “Undrained” shear strength: - apparent cohesion 3) Shear failure behaviour: - contractive, dilative, collapsive
    [Show full text]
  • Weathering, Erosion, and Susceptibility to Weathering Henri Robert George Kenneth Hack
    Weathering, erosion, and susceptibility to weathering Henri Robert George Kenneth Hack To cite this version: Henri Robert George Kenneth Hack. Weathering, erosion, and susceptibility to weathering. Kanji, Milton; He, Manchao; Ribeira e Sousa, Luis. Soft Rock Mechanics and Engineering, Springer Inter- national Publishing, pp.291-333, 2020, 9783030294779. 10.1007/978-3-030-29477-9. hal-03096505 HAL Id: hal-03096505 https://hal.archives-ouvertes.fr/hal-03096505 Submitted on 5 Jan 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Published in: Hack, H.R.G.K., 2020. Weathering, erosion and susceptibility to weathering. 1 In: Kanji, M., He, M., Ribeira E Sousa, L. (Eds), Soft Rock Mechanics and Engineering, 1 ed, Ch. 11. Springer Nature Switzerland AG, Cham, Switzerland. ISBN: 9783030294779. DOI: 10.1007/978303029477-9_11. pp. 291-333. Weathering, erosion, and susceptibility to weathering H. Robert G.K. Hack Engineering Geology, ESA, Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente Enschede, The Netherlands e-mail: [email protected] phone: +31624505442 Abstract: Soft grounds are often the result of weathering. Weathering is the chemical and physical change in time of ground under influence of atmosphere, hydrosphere, cryosphere, biosphere, and nuclear radiation (temperature, rain, circulating groundwater, vegetation, etc.).
    [Show full text]
  • Correlating Foreland Basin Subsidence with Eclogite Metamorphism
    ATI..ANTic GEOLOGY 79 Loading the Laurentian margin: correlating foreland basin subsidence with eclogite metamorphism 2 3 4 John WF. Waldron•, R.A. Jamieson , G.S. Stockmal and L.A. Quinn 1Geology Department, Saint Mary '.S' University, Halifax, Nova Scotia B3H 3C3, Canada 'Department ofEarth Sciences, Dalhousie University, Halifax, Nova Scotia B3H 3J5, Canada 1Geological Survey of Canada (Calgary), 3303-33rd Street Northwest, Calgary, Alberta T2L 2A 7, Canada 'Department ofGeology, Brandon University, Brandon, Manitoba R7A 6A9, Canada Paleozoic loading of the former Laurentian continental de Lys Supergroup) are exposed in the Baie Verte Peninsula margin is recorded both in the subsidence history of the Ap­ and elsewhere. These units record Barrovian metamorphism palachian foreland basin and in metamorphic rocks now ex­ with peak temperatures around 700 to 750°C at 7 to 9 kbar; humed in internal parts of the Newfoundland Humber zone. isotopic data indicate that peak temperatures were reached in The Cambrian-Ordovician passive margin ofLaurentia Early Silurian time ('Salinian orogeny'), followed by rapid ex­ underwent a transition to a foreland basin setting beginning humation. Amphibolite facies metamorphism overprints an in Early Ordovician time. Middle Ordovician ('Taconian ') foreland earlier eclogite facies assemblage, for which minimum pres­ basin sediments (Table Head and Goose Tickle groups), in sures of 1.2 GPa at 500°C require burial of the Laurentian part derived from the Humber Arm Allochthon, are relatively margin beneath at least 40 km of overburden, which may have thin (ca. 250 m in offshore industry seismic data, thinning to included thrust sheets of continental margin rocks and the west).
    [Show full text]
  • Geology and Seismicity
    SECTIONNINE GEOLOGY AND SEISMICITY 9. Section 9 NINE Geology and Seismicity This section describes the major geologic regions that could be affected by project construction and operation and the potential environmental consequences of the alternatives. 9.1 AFFECTED ENVIRONMENT The following paragraphs summarize the geologic conditions and hazards that may be encountered during the construction and implementation of the alternatives for the San Luis Drainage Feature Re-evaluation. The geologic environment is discussed in greater detail in Appendix H. The focus of this section is the geologic and seismic characteristics of the Great Valley and the Coast Ranges geomorphic provinces, which may influence the comparison of a the action alternatives due to the geologic conditions and potential geologic hazards associated with these regions. 9.1.1 Regulatory Background Several Federal and State regulations govern geology, seismicity, and soils in California. The Federal actions include the Earthquake Hazard Reduction Act of 1977, Executive Order 12699 on Seismic Safety of Federal Buildings, and the Uniform Building Code (superceded in California by the California Building Code). The State actions include the Alquist-Priolo Act, the Field Act, the California Building Code, and the Seismic Hazards Mapping Act. Some State agencies, including California Department of Transportation (Caltrans) and California Department of Water Resources (DWR), Division of Safety of Dams, have their own actions covering seismic and geologic hazards. In addition, municipalities and counties can have general or specific plans that may include the need for permitting. The regulatory background governing geology, seismicity, and soils is discussed further in Section 4.6. SLDFR Final EIS Section 09_Geology 9-1 SECTIONNINE Geology and Seismicity 9.1.2 Geologic Setting The existing San Luis Drain is situated near the western margin of San Joaquin Valley (Figure 9-1), which comprises the southern region of the Great Valley geomorphic province (Harden 1998).
    [Show full text]
  • Types of Landslides.Indd
    Landslide Types and Processes andslides in the United States occur in all 50 States. The primary regions of landslide occurrence and potential are the coastal and mountainous areas of California, Oregon, Land Washington, the States comprising the intermountain west, and the mountainous and hilly regions of the Eastern United States. Alaska and Hawaii also experience all types of landslides. Landslides in the United States cause approximately $3.5 billion (year 2001 dollars) in dam- age, and kill between 25 and 50 people annually. Casualties in the United States are primar- ily caused by rockfalls, rock slides, and debris flows. Worldwide, landslides occur and cause thousands of casualties and billions in monetary losses annually. The information in this publication provides an introductory primer on understanding basic scientific facts about landslides—the different types of landslides, how they are initiated, and some basic information about how they can begin to be managed as a hazard. TYPES OF LANDSLIDES porate additional variables, such as the rate of movement and the water, air, or ice content of The term “landslide” describes a wide variety the landslide material. of processes that result in the downward and outward movement of slope-forming materials Although landslides are primarily associ- including rock, soil, artificial fill, or a com- ated with mountainous regions, they can bination of these. The materials may move also occur in areas of generally low relief. In by falling, toppling, sliding, spreading, or low-relief areas, landslides occur as cut-and- La Conchita, coastal area of southern Califor- flowing. Figure 1 shows a graphic illustration fill failures (roadway and building excava- nia.
    [Show full text]
  • South Fork Coquille Watershed Analysis
    DOCUMENT A 13.66/2: COQUILLE fiVE, LOWER S.F. 17 10 03 00* I C 66x 1 COQUILLE RIVER, UPPER S.F 17 1:-03 01* ' United States Q, '0) Departimnt of Agriculture THIS PUBLICATION Forest Serilce CMN FE CHECKED OUT Pacific Northwest Region 1995 JA* fSouth Fork Coquille Wate1hed Analysis Iteration 1.0 Powers Ranger Distric, Slsklyou National Forest September 1995 SOUTHERN OREGON UNWVERSiTY LIBRARY ASHLAND, OREGON 97520 United Stat. Depaenent of Agnculure Forest Service Pacific Northwest Region 1995 SOUTH FORK COQUILLE WATERSHED ANALYSIS ITERATION 1.0 I have read this analysis and it meets the Standards and Guidelines for watershed analysis required by an amendment to the Forest Plan (Record of Decision dated April 1994). Any additional evidence needed to make a decision will be gathered site-specifically as part of a NEPA document or as an update to this document. SIGNED CoQ 4 DATE q 1T2 letE District Ranger Powers Ranger District Siskiyou National Forest South Fork Coquille Watershed Analysis - September 1995 Developed by Interdisciplinary Team Members: Steve Harbert Team leader Betsy Howell Wildlife Biologist Dave Shea Botantist, Wildlife Biologist Ruth Sisko Forester Cindy Ricks Geologist Chris Parks Hydrologist Max Yager Fish Biologist Kathy Helm Writer-Editor (March-April 1995), BLM Tina Harbert Writer-Editor (May-July 1995), Powers R.D. Joe Hallett Cultural Resource Key Support: Joel King Forest Planner, Siskiyou National Forest Sue Olson Acting District Ranger, Powers R.D. (Jan-May 1995) Carl Linderman District Ranger, Powers R.D. Marshall Foster GIS, Powers R.D. Jodi Shorb Computer Assistant Linda Spencer Computer Support For Further Information, contact: Powers Ranger District Powers, OR 97466 (503) 439-3011 The policy of the United States Department of Agriculture Forest Service prohibits discrimination on the basis of race, color, national origin, age, religion, sex, or disability, familial status, or political affiliation.
    [Show full text]
  • Slope Stability 101 Basic Concepts and NOT for Final Design Purposes! Slope Stability Analysis Basics
    Slope Stability 101 Basic Concepts and NOT for Final Design Purposes! Slope Stability Analysis Basics Shear Strength of Soils Ability of soil to resist sliding on itself on the slope Angle of Repose definition n1. the maximum angle to the horizontal at which rocks, soil, etc, will remain without sliding Shear Strength Parameters and Soils Info Φ angle of internal friction C cohesion (clays are cohesive and sands are non-cohesive) Θ slope angle γ unit weight of soil Internal Angles of Friction Estimates for our use in example Silty sand Φ = 25 degrees Loose sand Φ = 30 degrees Medium to Dense sand Φ = 35 degrees Rock Riprap Φ = 40 degrees Slope Stability Analysis Basics Explore Site Geology Characterize soil shear strength Construct slope stability model Establish seepage and groundwater conditions Select loading condition Locate critical failure surface Iterate until minimum Factor of Safety (FS) is achieved Rules of Thumb and “Easy” Method of Estimating Slope Stability Geology and Soils Information Needed (from site or soils database) Check appropriate loading conditions (seeps, rapid drawdown, fluctuating water levels, flows) Select values to input for Φ and C Locate water table in slope (critical for evaluation!) 2:1 slopes are typically stable for less than 15 foot heights Note whether or not existing slopes are vegetated and stable Plan for a factor of safety (hazards evaluation) FS between 1.4 and 1.5 is typically adequate for our purposes No Flow Slope Stability Analysis FS = tan Φ / tan Θ Where Φ is the effective
    [Show full text]
  • Cohesion Development in Disrupted Soils As Affected by Clay and Organic Matter Content and Temperature'
    463 Reprinted from the Soil Science Society of America Journal Volume 51, no. 4. July-August 1987 677 South Segos Rd., Madmon, WI 53711 USA Cohesion Development in Disrupted Soils as Affected by Clay and Organic Matter Content and Temperature' w. D. KEMPER, R. C. ROSENAU, AND A. R. DEXTER 2 ABSTRACT OIL STRUCTURE IS DISRUPTED and bonds holding Soils were dispersed and separated into sand, silt, and clay frac- S particles together are broken frequently as soil is tions that were reconstituted to give mixtures of each soil with 5 to frozen at high water contents, wetted quickly, tilled, 40% clay. In the range from 0 to 35% clay, higher clay contents or compacted (e.g., Bullock et al, 1987). As soils dry, resulted in greater stability. Rate of cohesion recovery was over 10 increasing tension or negative pressure in the water times as fast at 90°C as it was at 23°C, showing that the processes (Briggs, 1950) pulls particles together, increasing the Involved are physical-chemical rather than biological. Maximum rates number of contact points at which bonding can take of cohesion recovery occurred at moderate soil water tensions, prob- place in newly disrupted soils. Strengths of aggregates ably because some tension is needed to pull the particles into direct formed from disrupted soils increase with time (Blake contact, but a continuous water phase is also essential to allow dif- and Oilman, 1970; Utomo and Dexter, 1981; Kemper fusion of bonding agents to the contact points. Since diffusion rates and Rosenau, 1984), even when water content re- in water increase 3e0o*, while rate of cohesion recovery increased mains constant, indicating increasing strength of par- 1000% when temperature was raised from 23 to 90°C, other factors, ticle-to-particle bonds.
    [Show full text]