Surficial geologic map of the Roanoke Rapids 30' x 60' quadrangle, North Carolina

Weems, Robert E.; Lewis, William C.; Aleman-Gonzalez, W.

doi:10.3133/ofr20091149

Cited by 4 publications

(3 citation statements)

References 11 publications

(18 reference statements)

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“…The surface soil consists of Quaternary alluvium with Miocene and Upper Cretaceous sedimentary materials underlying the alluvium soil layer [11,12]. Unconsolidated fine sands, silts, and clays are the primary materials, but there are also clayey Miocene deposits in places [12][13][14]. Three significant reservoirs-Kerr Lake, Lake Gaston, and Roanoke Rapids Lake-were created after the construction of Kerr Dam, Gaston Dam, and Roanoke Rapids Dam, respectively.…”

Section: Study Sitesmentioning

confidence: 99%

“…The soil profile at each riverbank was established by visual observation and in situ tests in the field and laboratory tests using soil samples obtained from vertical auger holes. The hand auger was capable of drilling to depths of up to about 3 m. By drilling at several locations along the bank slope, the soil profile was identified to a depth of 6 m. Given that soil layers deeper than 6 m from the bank top could not be visually identified even during low flow, the thickness of the lowest soil layer below 6 m was assumed based on previous reports in the literature [13,14]. The riverbanks' vertical soil profile was simplified using between three and five soil layers, including the assumed bottom impervious layer for modeling purposes.…”

Section: Riverbank Geometry and Soil Profilementioning

confidence: 99%

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Laboratory and In Situ Determination of Hydraulic Conductivity and Their Validity in Transient Seepage Analysis

Nam

Gutierrez

Diplas

et al. 2021

Water

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This paper critically compares the use of laboratory tests against in situ tests combined with numerical seepage modeling to determine the hydraulic conductivity of natural soil deposits. Laboratory determination of hydraulic conductivity used the constant head permeability and oedometer tests on undisturbed Shelby tube and block soil samples. The auger hole method and Guelph permeameter tests were performed in the field. Groundwater table elevations in natural soil deposits with different hydraulic conductivity values were predicted using finite element seepage modeling and compared with field measurements to assess the various test results. Hydraulic conductivity values obtained by the auger hole method provide predictions that best match the groundwater table’s observed location at the field site. This observation indicates that hydraulic conductivity determined by the in situ test represents the actual conditions in the field better than that determined in a laboratory setting. The differences between the laboratory and in situ hydraulic conductivity values can be attributed to factors such as sample disturbance, soil anisotropy, fissures and cracks, and soil structure in addition to the conceptual and procedural differences in testing methods and effects of sample size.

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Section: Study Sitesmentioning

confidence: 99%

Section: Riverbank Geometry and Soil Profilementioning

confidence: 99%

Laboratory and In Situ Determination of Hydraulic Conductivity and Their Validity in Transient Seepage Analysis

Nam

Gutierrez

Diplas

et al. 2021

Water

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show abstract

“…Surface soil in the area is primarily Quaternary alluvium deposits up to 7.6 m depth, with Upper Cretaceous sedimentary materials underlying the alluvium soil layer [10]. A loose layer of silty sand exists at the top of the riverbank, and a firm and thick cohesive soil layer underlies it.…”

Section: Soil Propertiesmentioning

confidence: 99%

Effects of Hydropower Dam Operation on Riverbank Stability

et al. 2021

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The increasing number of extreme climate events has impacted the operation of reservoirs, resulting in drastic changes in flow releases from reservoirs. Consequently, downstream riverbanks have experienced more rapid and frequent changes of the river water surface elevation (WSE). These changes in the WSE affect pore water pressures in riverbanks, directly influencing slope stability. This study presents an analysis of seepage and slope stability for riverbanks under the influence of steady-state, drawdown, and peaking operations of the Roanoke Rapids Hydropower dam on the lower Roanoke River, North Carolina, USA. Although the riverbanks were found to be stable under all the discharge conditions considered, which indicates that normal operations of the reservoir have no adverse effects on riverbank stability, the factor of safety decreases as the WSE decreases. When the role of fluvial erosion is considered, riverbank stability is found to reduce. Drawdown and fluctuation also decrease the safety factor, though the rate of the decrease depends more on the hydraulic conductivity of the soils rather than the discharge pattern.

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Determination of the shear strength of unsaturated soils using the multistage direct shear test

Nam

Gutierrez

Diplas

et al. 2011

Engineering Geology

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Surficial geologic map of the Roanoke Rapids 30' x 60' quadrangle, North Carolina

Cited by 4 publications

References 11 publications

Laboratory and In Situ Determination of Hydraulic Conductivity and Their Validity in Transient Seepage Analysis

Laboratory and In Situ Determination of Hydraulic Conductivity and Their Validity in Transient Seepage Analysis

Effects of Hydropower Dam Operation on Riverbank Stability

Determination of the shear strength of unsaturated soils using the multistage direct shear test

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