Date of Graduation

5-2012

Document Type

Thesis

Degree Name

Master of Arts in Geography (MA)

Degree Level

Graduate

Department

Geosciences

Advisor/Mentor

Dixon, John C.

Committee Member

Paradise, Thomas R.

Second Committee Member

Brye, Kristofor R.

Keywords

Health and environmental sciences; Social sciences; Earth sciences; Experiments; Geomorphology; Northwest arkansas; Slope failures; Slump

Abstract

Slope failure continues to pose risks to society because knowledge of environmental factors and their interactions are unclear and possibly misunderstood. This misunderstanding leads to generalizations about slope failure susceptibility mapping, despite knowing that slope failures are likely the result of an extensively complex set of interactions among a number of environmental, edaphic, and geomorphic characteristics. Therefore a series of experiments were conducted to investigate the effects of slope, soil texture, vegetation cover, bedrock permeability, and compaction,. A wooden flume with a slope face 1 m wide by 1.5 m long with a 10 cm toe was constructed to contain soil upon which simulated rainfall was applied. The length of time from the beginning of the simulated rainfall to visible evidence of slope failure was recorded and evaluated using analysis of variance.

Significant differences in time to failure were observed between different vegetation covers and soil textures, where the coarse-textured soil was generally less stable. Other treatments, including simulated bedrock permeability and slope angle, were also determined to have significant influences on time to failure, though trends among slope angle and bedrock permeability could not be described as generally positive or negative. Compaction significantly impacted time to failure when in combination with other factors, but not alone. Other observations were noted as they related to position of the slope failure on the slope face. The slope was less stable at localized thin points in the soil and points on the face at or above the midway point of the face. Field examination of shallow slope failures revealed trends such as localized thin points in the soil profile and the toe of the slope failure and localized thick points in the soil profile at the head. Slope failures occurred on backslopes and slope crests in the field. This study demonstrated that environmental factors work in conjunction with one another to stabilize or compromise slope stability and cannot be generally characterized as detrimental or beneficial. Based on rainfall simulation and actual field data, this study also demonstrated the complex interactions among environmental, edaphic, and geomorphic factors as they relate to slope stability.

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