Browsing by Author "Ozer, A. T."

Now showing 1 - 5 of 5

Citation Count: 14
Assessment of EPS block geofoam with internal drainage for sandy slopes subjected to seepage flow
(Ice Publishing, 2014) Akay, O.; Ozer, A. T.; Fox, G. A.
Lightweight expanded polystyrene (EPS) block geofoam (geofoam block) is commonly used as a replacement of the heavy in situ soil during slope remediation in order to reduce driving forces. The design procedure requires the use of permanent drainage systems to alleviate hydrostatic pressures in geofoam block slope systems. In this study, small-scale laboratory lysimeter experiments investigated the behavior of a stabilized sandy slope with a geofoam block slope system experiencing seepage. An internal drainage system was incorporated by grooving dual drainage channels (weep holes) on the top and bottom side of the geofoam blocks. A lysimeter with dimensions of 60 cm height, 20 cm width, and 200 cm length was constructed in the laboratory. Slopes were constructed by compacting sand. The geofoam blocks (2.5 cm height, 5 cm width, and 15 cm length) were placed on the sandy slope face with an angle of 458 in 'one row' and 'two rows' configurations. The experiments were conducted under constant water pressure heads (25-, 38-, and 50-cm pressure head boundary conditions) in the water reservoir located at the opposite end of the lysimeter from the geofoam blocks. In general, the lightweight geofoam blocks could not resist earth and hydrostatic pressures under seepage. The back-slope was not selfstable under seepage conditions, and deep-seated global stability failures were observed, except for the remediated slope at the 25-and 38-cm pressure head boundary conditions. The internal drainage system was ineffective at dissipating piezometric pressures at the higher seepage gradients investigated at this lysimeter scale. Numerical slope stability modeling confirmed these observations, predicting a factor of safety below the critical value for global stability in cases where failure was observed. More elaborate geofoam block configurations and/ or drainage systems should be used to increase resistance against global stability failure caused by higher seepage gradients.
Citation Count: 3
CPTU and DMT for estimating soil unit weight of Lake Bonneville clay
(Crc Press-taylor & Francis Group, 2013) Ozer, A. T.; Bartlett, S. F.; Lawton, E. C.
This paper discusses the use of piezecone penetration test (CPTU) and flat-plate dilatometer (DMT) for estimating the soil unit weight of the Lake Bonneville clay in Salt Lake City, Utah. Soil unit weight is required when calculating net cone resistance, normalized cone resistance, pore pressure ratio, and normalized friction ratio from CPTU results, and horizontal stress index from DMT results. To improve the predictive performances of existing correlations additional analysis were carried out. This is accomplished by correlating CPTU and DMT parameters with results obtained from high quality undisturbed sampling using Multiple Linear Regression (MLR) analyses to develop correlations for soil unit weight. MLR analyses showed that the both CPTU and DMT can reasonably estimate the soil unit weight of the relatively soft, Lake Bonneville clay deposits with CPTU giving slightly higher predictive performance. Proposed correlations emerged for estimation of total unit weight in terms of net cone resistance and sleeve friction from CPTU results and P1 value of DMT. By obtaining reliable estimates of soil unit weight directly from CPTU and DMT results, geotechnical consultants in the Salt Lake Valley would gain benefit for efficient post-processing of the both CPTU and DMT data.
Citation Count: 30
Effects of EPS bead inclusions on stress-strain behaviour of sand
(Ice Publishing, 2014) Edincliler, A.; Ozer, A. T.
Lightweight fill solutions have been used in many civil engineering projects throughout the world. At locations with poor soil conditions, alternative lightweight construction fill materials such as expanded polystyrene (EPS) geofoam, wood chips, and tyre wastes may be used instead of conventional fill materials. These materials are used as an additive for the soil. It is known that the type, aspect ratio and content of the admixtures have an important role in the mechanical properties of the mixtures. The main objective of this study was to assess the feasibility of the potential use of EPS beads in geotechnical applications. The effect of EPS bead gradation on the stress-strain behaviour of lightweight composite materials composed of EPS bead-sand mixtures (EPS-sand) was investigated through a series of triaxial compression tests under three different confining pressures. Three different types of spherical EPS beads with different unit weights (EPS-1, EPS-2, and EPS-3) were mixed with sand with varying EPS bead content. This study has shown that the deviatoric stress of a EPS-sand mixture is not only a function of volumetric EPS bead content but it also depends on EPS bead grain size distribution (EPS bead type). Whereas volumetric EPS bead content increases when all other variables are constant (EPS bead type in EPS-sand), the initial modulus of elasticity decreases linearly. Consequently, EPS bead inclusion did not enhance the maximum deviatoric stress of EPS-sand when compared with that of the sand-only specimen. However, bead addition provides a lightweight aspect to the mixture which can be attractive to use in many geotechnical engineering projects. EPS bead content, confining pressure and EPS bead type-dependent multiple linear regression (MLR) equations were proposed to estimate the initial undrained elastic modulus of EPS-sand to reduce the cost and time involved in conventional laboratory testing of EPS-sand mixtures. Based on the stress-strain behaviour of EPS-sand, these mixtures may be utilised in geotechnical applications as a lightweight fill material.
Citation Count: 16
Laboratory study on the use of EPS-block geofoam for embankment widening
(Ice Publishing, 2016) Ozer, A. T.
The use of expanded polystyrene geofoam (geofoam block) has been gaining momentum in roadway expansion projects. They are traditionally placed along the slope face of the existing roadway embankment as a side-hill fill. However, previous studies have shown the detrimental effects of seepage forces on the side-hill fill type of geofoam block configurations. In order to improve the performance of traditional embankment-widening configuration under seepage forces, an alternative geofoam block assembly is proposed. For this purpose, a lysimeter with dimensions of 60 cm high, 20 cm wide, and 200 cm long was constructed in the laboratory. Awater reservoir located at the end of the lysimeter provided three different constant pressure heads (25 cm-, 38 cm-, and 50 cm-H2O pressure) during the tests. An embankment-widening geofoam block assembly was placed along the slope face of marginally stable sandy embankment to investigate the effects of seepage on the stability of geofoam block assembly. The dimensions of the geofoam blocks used to construct the embankment-widening sections were 2.5 cm high, 5 cm wide, and 15 cm long. In addition to the laboratory physical testing, factors of safety against global stability and hydrostatic sliding failures were studied through coupled numerical modelling. Stability modelling comprised fully coupled variably saturated flow and conventional limit equilibrium analysis to quantify the performance of the lysimeter test against global stability failure. Factor of safety against hydrostatic sliding was quantified using fully coupled variably saturated flow and stress-deformation modelling. Both laboratory and numerical models showed that the proposed geofoam block configuration significantly improved the performance of traditional side-hill fill embankment-widening technique under seepage forces.
Citation Count: 1
Protecting roller-compacted concrete armored emergency spillway against uplift with geocomposite drain: Loxahatchee Reservoir example
(Ice Publishing, 2012) Ozer, A. T.; Bromwell, L. G.
When designing a roller-compacted concrete (RCC) spillway for a reservoir, seepage-induced uplift pressures need to be considered. This case study describes the design, construction and post-construction performance of a drainage system consisting of a geocomposite drain immediately beneath a stair-stepped RCC spillway at the Loxahatchee Reservoir in western Palm Beach County, Florida, USA. The installation comprised 2.8 km of RCC and a geocomposite drain to construct the fixed-weir emergency spillway. The primary stability issue for the spillway was the development of excessive pore water pressure beneath the RCC in the event of rapid drawdown of the reservoir. Transient seepage analysis predicted that installation of the geocomposite drain would eliminate excess pore pressures beneath the RCC, and dramatically increase the factor of safety against uplift (increased from 0.5 to a value of the order of 6), preventing structural instability of the spillway. Since placing the reservoir in operation, no structural instability has been observed in the spillway. Also, the absence of excess pore pressure is predicted by post-construction transient seepage analysis using reservoir operational-stage data.