Browsing by Author "Bartlett, Steven F."

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Citation Count: 32
Behavior of sandy slopes remediated by EPS-block geofoam under seepage flow
(Elsevier Sci Ltd, 2013) Akay, Onur; Ozer, A. Tolga; Fox, Garey A.; Bartlett, Steven F.; Arellano, David
Expanded polystyrene (EPS) geofoam (geofoam block) is commonly used as a lightweight fill for many civil engineering applications. However, when used for slope remediation, the behavior of geofoam block for slope systems undergoing seepage flow is not well known. In this study, a total of 36 laboratory lysimeter experiments (dimensions of 60 cm height, 20 cm width, and 200 cm length) were conducted to investigate the behavior of sandy slopes containing geofoam blocks as a lightweight fill material. These experiments were conducted with three different values of constant water pressure in the water reservoir located at one end of the lysimeter. In addition, three different configurations of geofoam block were tested with geofoam blocks placed on the face of the packed sandy slope. The dimensions of the geofoam blocks were 2.5 cm high, 5 cm wide, and 15 cm long to achieve a 1:20 scale corresponding to actual block size that is commonly manufactured. Laboratory physical test results were quantified by coupled seepage flow and slope stability models showing the adverse effect of seepage on the factor of safety (FS). Geofoam block configurations were found to be stable against seepage conditions which would cause a shallow-seated failure of the slope in the absence of the geofoam blocks. This is due to the fact that the geofoam blocks could completely fill the mass of the existing slope material subjected to failure. However, the geofoam block configurations were unstable against seepage conditions that resulted in deep-seated failures of marginally stable, sand slopes. (C) 2013 Elsevier Ltd. All rights reserved.
Citation Count: 1
Comparison of Methodologies for Establishing Design Properties of Horizontal Drainage in Soft Cohesive Soils
(Natl Acad Sciences, 2015) Farnsworth, Clifton B.; Ozer, A. Tolga; Bartlett, Steven F.; Lawton, Evert C.
Estimating the rate of settlement for foundation soils treated with vertical drains requires an understanding of the horizontal drainage behavior of the soil, because the time of consolidation settlement may be critical to the overall construction schedule and sequencing. This paper provides a case study comparison of the results of methodologies associated with obtaining design parameters for horizontal drainage for use with vertical drain design, including backcalculation of field settlement data, cone penetrometer testing for pore pressure dissipation, and laboratory Rowe cell testing, by means of the soft, cohesive Lake Bonneville soil deposits in Salt Lake City, Utah. Each of these methodologies has an inherent set of strengths and limitations that should be considered when vertical drains are being designed or time of consolidation settlement is being estimated. Backcalculation of field performance data is effective in identifying true in situ settlement behavior but is not always feasible. Rowe cell testing tends to provide values that more closely correspond with those obtained from backcalculation but is not often performed. Testing for pore pressure dissipation is the most used technique, but it can provide drainage values much higher than the other two methodologies.
Citation Count: 23
A new method for remediation of sandy slopes susceptible to seepage flow using EPS-block geofoam
(Elsevier Sci Ltd, 2014) Ozer, A. Tolga; Akay, Onur; Fox, Garey A.; Bartlett, Steven F.; Arellano, David
Using expanded polystyrene (EPS) geofoam (geofoam block) in slope remediation projects has drawn interest from the civil engineering sector for its ease of application and budget saving features. According to design precedence, all slope remediation applications that use geofoam blocks should incorporate permanent drainage systems to prevent instability of the lightweight geofoam blocks due to hydrostatic and seepage pressures. In this study, a new method for slope remediation using geofoam blocks was tested through physical laboratory experiments. For this purpose, a total of 24 lysimeter (dimensions of 60 cm height, 20 cm width, and 200 cm length) experiments (including duplicates) were conducted in which seepage through a geofoam block slope system were generated with three different constant water levels in the water reservoir of the lysimeter. Geofoam blocks (dimensions of 2.5 cm height, 5 cm width, and 15 cm length) were assembled to form embankment type configuration at the toe section of the sandy slopes. This study also included coupled numerical model simulations that were comprised of variably saturated flow modeling and slope stability modeling which could be implemented successfully for the global static failure analysis of the geofoam block slope system comprised of two mediums with different geotechnical characteristics. In addition to global static stability failure analysis, which involved conventional limit equilibrium analysis for the geofoam block slope system, hydrostatic sliding mechanism was investigated which provided insight into using an overburden concept to increase the resistance against horizontal driving forces. Experimental and numerical modeling results showed that the geofoam block slope system was stable even though the phreatic surface was above the bottom of the geofoam block assemblage. For this reason, the embankment type configuration tested in this study can be considered a viable remediation technique where seepage induced deep-seated global stability and hydrostatic sliding failures are a concern. (C) 2014 Elsevier Ltd. All rights reserved.
Citation Count: 17
New method to determine proper strain rate for constant rate-of-strain consolidation tests
(Canadian Science Publishing, Nrc Research Press, 2012) Ozer, A. Tolga; Lawton, Evert C.; Bartlett, Steven F.
The development of a new semiempirical method to predict the proper strain rate for constant rate-of-strain (CRS) consolidation tests is described herein. The validity of the proposed method is analyzed using experimental results from CRS and incremental loading tests on four types of soil: Lake Bonneville clay, Massena clay, kaolinite, and montmorillonite. It is found that the maximum allowable strain rate depends on the initial void ratio of the soil and thus is related to the compressibility of the soil. The effect of the strain rate on the distribution of the pore pressure within the sample is investigated by comparing values of effective vertical stress calculated using a linear equation published by Wissa et al. in 1971 with values of effective stress at the base of the specimen determined from measured values of pore pressure. Overall, the proposed method predicts the maximum allowable strain rate very well for three of the four soils and moderately well for the other soil.