Slope Stability of the Hunter Creek Formation: A Geotechnical Investigation Near Mogul, Nevada
AuthorMiller, Barry C.
AdvisorWatters, Robert J.
Geological Sciences and Engineering
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The Hunter Creek sandstone near Mogul, Nevada, is a Neogene sedimentary unit in the Verdi basin consisting of fluvial, deltaic, and lacustrine facies. Numerous slope failures have occurred in the unit mostly along streams, canals, and the Truckee River. Field mapping showed that most of the slope failures occur south of Interstate 80 between Verdi and northwest Reno, Nevada.Four landslides were studied and analyzed south of I-80. Field work included failure mapping, obtaining bedding orientations, and sample collection for laboratory testing. A monument was placed in an active failing mass to track movement over the spring of 2012 annual snow-melt. Laboratory testing included particle size distribution, specific gravity, Atterberg limits, and direct shear testing. An engineering stratigraphic column was created comparing particle size with friction angle and the plasticity of the soils.The four slope failures were modeled using the computer program SLIDE. Each slope was modeled to represent spring thaw conditions with a high groundwater level and an analysis was performed on each slope to determine the sensitivity of the factor of safety with drops in water levels. Two failure criteria were used in modeling: the Coulomb failure criterion and the Hoek-Brown failure criterion. The analyses confirmed that the slopes in these units are close to failure (FS > 1.0) as a result of low friction values and cohesion. Residential development south of I-80 is likely to continue, so the slopes were modeled showing a cut and fill typical of areas developed on sloped terrain. Analyses confirmed that surcharges from regrading combined with high water level conditions would lead to slope failure. The study area is also seismically active and the cut and fill model was analyzed to determine stability problems during earthquakes.