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VARIATION OF GEOTECHNICAL STRENGTH PROPERTIES WITH AGE OF LANDFILLS ACCEPTING BIOSOLIDS
Title
VARIATION OF GEOTECHNICAL STRENGTH PROPERTIES WITH AGE OF LANDFILLS ACCEPTING BIOSOLIDS.
Creator
Pinapati, Kishore, Chopra, Manoj, University of Central Florida
Abstract / Description
The solid portion of waste disposal, known as Municipal Solid Waste (MSW) can be landfilled. Landfilling has proved to be a safe, sanitary and economical method of disposal. A by-product from wastewater treatment plants called biosolids is sometimes co-disposed along with MSW in landfills. Recent work at the University of Central Florida has focused on the behavior of the mixture of MSW and biosolids. As an increased amount of waste accumulates in these landfills, it creates a new problem &...
Show moreThe solid portion of waste disposal, known as Municipal Solid Waste (MSW) can be landfilled. Landfilling has proved to be a safe, sanitary and economical method of disposal. A by-product from wastewater treatment plants called biosolids is sometimes co-disposed along with MSW in landfills. Recent work at the University of Central Florida has focused on the behavior of the mixture of MSW and biosolids. As an increased amount of waste accumulates in these landfills, it creates a new problem – the geotechnical stability of landfills. In current literature, classical geotechnical testing methods have been followed to find the strength properties of these landfill materials. Furthermore, geotechnical methods of slope stability analyses have been employed to determine the stability of landfill slopes. As these materials have a high organic content, their strength properties may potentially change with time because of the decay of the organic materials. In the present work, an attempt is made to monitor the change in the geotechnical strength properties of the landfill materials as a function of time. Direct shear tests used for soil testing, with some modifications, were performed on cured compost samples of MSW mixed with biosolids. Geotechnical strength properties of these cured samples were compared to those of an artificially prepared mixture of MSW and biosolids, from the published literature. In addition, direct shear tests are also performed to find the interface properties of a geonet with the cured samples to check the role of a geonet in reinforcing the landfill slopes. A slope stability analysis software SLOPE/W is used to analyze the stability of the landfills. Cohesion is observed to decrease with time while the friction angle increases with time. Stability (the factor of safety against failure) of landfill slopes increases with time due to increased effective stresses and increased friction angle, as the organic material decays. This may result in additional subsidence but an increase in the effective shear strength with time. Based on the interface test results and subsequent slope stability analyses, it is found that the inclusion of a geonet improves the slope stability of a landfill. This could be a potential benefit to the landfill as reinforcement if properly placed. Based on the slope stability analysis on landfills with different slopes, it is concluded that the slope stability of a landfill is improved by keeping the slopes less steep.
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Date Issued
2006
Identifier
CFE0000919, ucf:46758
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000919
USE OF VEGETATIVE MULCH AS DAILY AND INTERMEDIATE LANDFILL COVER
Title
USE OF VEGETATIVE MULCH AS DAILY AND INTERMEDIATE LANDFILL COVER.
Creator
Haddad, Assal, Reinhart, Debra, University of Central Florida
Abstract / Description
Management of yard waste is a significant challenge in the US, where in 2008 13.2% of the 250 million tons of municipal solid waste (MSW) was reported to be yard waste. This study describes research conducted in the laboratory and field to examine the application of vegetative mulch as daily and intermediate landfill cover. Mulch was found to exhibit stronger physical properties than soil, leading to a more stable landfill slope. Compaction of mulch was found to be significantly greater than...
Show moreManagement of yard waste is a significant challenge in the US, where in 2008 13.2% of the 250 million tons of municipal solid waste (MSW) was reported to be yard waste. This study describes research conducted in the laboratory and field to examine the application of vegetative mulch as daily and intermediate landfill cover. Mulch was found to exhibit stronger physical properties than soil, leading to a more stable landfill slope. Compaction of mulch was found to be significantly greater than soil, potentially resulting in airspace recovery. Degradation of mulch produced a soil-like material; degradation resulted in lower physical strength and hydraulic conductivity and higher bulk density when compared with fresh mulch. Mulch covers in the field permitted higher infiltration rates at high rain intensities than soil covers, and also generated less runoff due to greater porosity and hydraulic conductivity as compared to soil. Mulch covers appear to promote methane oxidation more than soil covers, although it should be noted that methane input to mulch covers was more than an order of magnitude greater than to soil plots. Life cycle assessment (LCA) showed that, considering carbon sequestration, use of green waste as landfill cover saves GHG emissions and is a better environmental management option compared to composting and use of green waste as biofuel.
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Date Issued
2011
Identifier
CFE0003605, ucf:48880
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0003605
SLOPE STABILITY ANALYSIS OF CLASS I LANDFILLS WITH CO DISPOSAL OF BIOSOLIDS USING FIELD TEST DATA
Title
SLOPE STABILITY ANALYSIS OF CLASS I LANDFILLS WITH CO DISPOSAL OF BIOSOLIDS USING FIELD TEST DATA.
Creator
Vajirkar, Mrutyunjay, Chopra, Dr. Manoj, University of Central Florida
Abstract / Description
Land filling provides a major, safe, and economical disposal route for biosolids and sludges. With an expanding world, the demand for larger and higher capacity landfills is rapidly increasing. Proper analysis and design on such fills have pushed the boundaries of geotechnical engineering practice, in terms of proper identification and assessment of strength and deformation characteristics of waste materials. The engineering properties of Municipal Solid Waste (MSW) with co-disposal of...
Show moreLand filling provides a major, safe, and economical disposal route for biosolids and sludges. With an expanding world, the demand for larger and higher capacity landfills is rapidly increasing. Proper analysis and design on such fills have pushed the boundaries of geotechnical engineering practice, in terms of proper identification and assessment of strength and deformation characteristics of waste materials. The engineering properties of Municipal Solid Waste (MSW) with co-disposal of biosolids and sludges with regards to moisture characteristics and geotechnical stability are of utmost importance. Significant changes in the composition and characteristics of landfill may take place with the addition of sludges and biosolids. In particular, the stability of waste slopes needs to be investigated, which involves the evaluation of the strength properties of the mixture of the waste and biosolids. This thesis deals with impact of the addition of biosolids on the geotechnical properties of class I landfill as determined from field investigations. The geotechnical properties are evaluated using an in-situ deep exploration test, called the Cone Penetration Test (CPT). CPT provides a continuous log of subsurface material properties using two measuring mechanisms, namely, tip resistance and side friction. The areas receiving biosolids are compared with areas without, to evaluate the effect of landfilling of biosolids. The required geotechnical shear strength parameters (angle of internal friction and cohesion) of MSW and biosolids mixture are determined by correlation with CPT results similar to the procedure followed in evaluating soil properties. The shear strength parameters obtained from the CPT data are then used to study the stability of different slope configurations of the landfill. The slope stability analysis is conducted on the various landfill models using the computer software SLOPE/W. This software was designed for soils but was found to be suitable for modeling landfills, as the waste is assumed to act similar to a cohesionless soil. Based on the field investigations, the angle of internal friction was found to be about 29° and the determination of any cohesion was not possible. It was concluded that the most suitable practical solution to adding biosolids into the landfill was in the form of trenches. From the slope stability study, it was found that the factor of safety reduces significantly with the introduction of biosolids due to a reduction in shear strength and increase in the overall moisture content. From a parametric study, the stability of a 1:2 side slope with an angle of friction lower than about 20° was found to be less than the safe limit of 1.5. In addition, the factors of safety for landfills with trenches extending close to the edges of the slopes were also found to be unsafe and this situation needs to be avoided in practice.
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Date Issued
2004
Identifier
CFE0000301, ucf:46313
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000301
Seepage and Stability Analysis of the Earth Dams under Drawdown Conditions by using the Finite Element Method
Title
Seepage and Stability Analysis of the Earth Dams under Drawdown Conditions by using the Finite Element Method.
Creator
Al-Labban, Salama, Chopra, Manoj, Mackie, Kevin, Wang, Dingbao, Elshennawy, Ahmad, University of Central Florida
Abstract / Description
One of the major concerns in the behavior of an earth dam is the change in the exit gradient and the impact on the slope stability under drawdown conditions. Drawdown can cause increased seepage forces on the upstream slope which may result in the movement of soil particles in the flow direction and cause erosion problems. In this research, a numerical approach, based on the finite element method (FEM) is used to analyze the seepage through the dam and its foundation to study exit gradients...
Show moreOne of the major concerns in the behavior of an earth dam is the change in the exit gradient and the impact on the slope stability under drawdown conditions. Drawdown can cause increased seepage forces on the upstream slope which may result in the movement of soil particles in the flow direction and cause erosion problems. In this research, a numerical approach, based on the finite element method (FEM) is used to analyze the seepage through the dam and its foundation to study exit gradients and slope stability under both steady-state and transient conditions. The results show that a central core is important in reducing the flux through the dam. Constructing a cutoff under the core further increases the efficiency of the core and lowers the phreatic line. However, it is seen that the submerged weight increases when the earth dam with a core or with a complete cutoff which causes higher water flux to flow out of the dam under the drawdown condition. The exit gradient at the upstream slope may reach critical levels and cause failure of the dam due to erosion. Adding an upstream filter is studied as a possible solution to this problem. Two configurations of the filters are modeled and the slope filter configuration performed best in reducing the exit gradient at the upstream face. A low permeability core with a cutoff increases deformation of the soil because of increased saturated areas in the upstream region. The factor of safety of the slope is also reduced because of the increased buoyancy of the soil at the upstream side of the dam. The soil properties of the upstream filter have a significant influence on the slope stability against sliding. An upstream slope filter increases the stability of the slope while a central filter decreases it.
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Date Issued
2018
Identifier
CFE0007303, ucf:52167
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007303