Thesis
Combined hydrology and slope stability assessment of the Olympic region of Washington State
Washington State University
Master of Science (MS), Washington State University
2011
Handle:
https://hdl.handle.net/2376/102856
Abstract
Landslides constitute a major geological hazard in the world due to their high financial cost and their nondiscriminatory nature. The Olympic Region of Washington State has many potential triggers of landslides, but prolonged periods of high rainfall is the most commonly attributed trigger of landslides. The current state of practice for landslide prediction is to assume pore water pressure above the phreatic surface is negligible; this methodology is incapable of accurately forecasting shallow landslides where suction plays a critical role. Suction varies with moisture content and as such a hydrological model that can be prescribed with varying vegetation and climate realizations should be used along with a stability model that includes soil suction to better predict shallow landslides. This study presents a methodology to predict the stability of shallow planar slope failures that incorporates the hydrologic modeling capabilities of the program Combined/Hydrology And Slope Stability (CHASM). An infinite limit equilibrium stability model that includes the effects of soil suction is developed for this purpose. The hydrologic model predicts the water conditions above and below the phreatic surface while the incorporation of soil suction more accurately predicts the shear strength of the soil above the phreatic surface. The methodology was shown to be effective in predicting slope failures above the phreatic surface during two simulations that were carried out for the Olympic Region (Queets River Slope and Clallam Slope). Utilizing rainfall data from the December 2007 storm event, failure was predicted above the phreatic surface around the 24th hour since rainfall for the Queets River Slope and around the 74th hour for the Clallam River Slope. Finally, design charts were developed for determination of the critical rainfall event for given slope angles and vegetative covers. The design charts predict failure in a 60 degree Hyas Gravelly Loam slope immediately after timber harvest if rainfall reaches 67- milimeters (2.6-inches) in a 24 hour period. These charts are intended for use by both engineers and land management personnel to manage and predict slope failures in the timber harvested Olympic Region of Washington State.
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Details
- Title
- Combined hydrology and slope stability assessment of the Olympic region of Washington State
- Creators
- Craig Abram Jordan
- Contributors
- Balasingam Muhunthan (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Civil and Environmental Engineering, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525040001842
- Language
- English
- Resource Type
- Thesis