Use of Instrumented Test Fill to Assess Static Liquefaction of Impounded Fly Ash

2016

Landfilling is the most common method ofsolid waste management in our country. Lining systems for waste containment facilities can be enhanced if they are constructed with reactive materials, that is, materials that retard the movement of solutes, promote biodegradation, or induce chemical conversion. One potential material for constructing reactive liners is Fly ash from coal-fired power plants that contains a modest amount of residual organic carbon, which is a sorbent of VOCs. In this study fly ash is taken into consideration and tested for various parameters associated with the behaviour of hydraulic barriers in landfills to advocate its usability as hydraulic barriers in landfills. Also, the hydraulic conductivity of fly ash decreases with addition of certain additives like lime, cement etc.

World of Coal Ash (WOCA …, 2007

An experimental and analytical investigation of the liquefaction potential of Class F fly ash is presented. The fly ash, originally placed in a 45 hectares impoundment, varied in depth from about 15 to 55 m. The proposed use for the ash was as a base for a utility monofill. The evaluation included cyclic triaxial tests performed on reconstituted fly ash samples at different densities, confining stresses and cyclic stress ratios representative of the impounded material and the seismic environment. Post-liquefaction strengths were measured by reconsolidating the samples at the initial effective confining stress and performing consolidated undrained (CU) triaxial tests. The measured cyclic strength was compared with the seismically induced stresses in the profile using the well known one dimensional wave propagation program SHAKE. The cyclic loadings imposed on the ash by the design earthquakes were found to be lower than the measured cyclic strength of the fly ash material.

Water Science and Technology, 2017

Depending on the usage of fly ash, it is necessary to determine its environmental parameters, such as the potential for pollutant transport/leaching after its built-in. This study presents a methodology for determination of transport parameters (filtration coefficient, effective porosity, longitudinal dispersivity, and the mean residence time) from experimental data collected from column experiments with a conservative tracer on different mixtures of fly ash with stabilizers (4.8% lime and 5% cement). The transport parameters are determined using (1) numerical model results and (2) an adapted analytical solution results against measured outflow tracer concentrations. The study shows that the addition of stabilizers decreases the filtration coefficient by an order of magnitude and the effective porosity by half. The longitudinal dispersivity is not influenced by the addition of lime to the mixture, and is increased by 40% by the addition of cement. The pollutant contact time with fly ash increases by six or nine times with the addition of lime and cement, respectively. The adaptation of the analytical solution agrees well with both the numerical solution and the experimental results, and it is anticipated to be of high value for determination of transport parameters for practitioners not familiar with numerical methods.

International Journal of Geosynthetics and Ground Engineering, 2015

Cement was added to class F type of fly ash in the proportion of 0, 2, 5 and 10 % to study for its suitability as a landfill liner material. Mixtures were compacted to their optimum moisture content (OMC) and maximum dry density (MDD). The results from the consolidation tests showed a relatively lower value of compression index for all the mixtures indicating the settlement due to application of overburden pressure would be small. Hydraulic conductivity of the samples were found to be decreased with the increasing the load. However, none of the mixtures exhibited a hydraulic conductivity value less than 10-9 m/s, a limiting criterion set by various environmental agencies for the material to be used as a landfill liner. However, mixtures of 90 % fly ash ? 10 % cement compacted at 5 % wet of OMC-MDD exhibited a hydraulic conductivity value less than 10-9 m/s. On drying, all the mixtures shrunk marginally. The unconsolidated undrained test results indicated that the shear strength parameters increase with increase in the cement content in the mixtures.

2007

Flowable fill, also known as Controlled Low Strength Material (CLSM), is used in place of ordinary geotechnical fill in construction applications. Fly ash playDue to the addition of air quality controls on coal-fired power plants, fly ash characteristics have an increasing amount of free carbon, ammonia, and/or lime residue. This results in more fly ash being disposed in landfills than being beneficially used. This paper presents the results of a laboratory study that has as objectives 1) to produce excavatable flowable fill with maximum ash incorporation (i.e., maximum amount of variable quality fly ash, minimum amount of Portland cement, and no sand) and 2) to determine the effect of different types of fly ash on the engineering properties of the flowable fills. The fly ashes evaluated for this project differ based on carbon, ammonia, and lime content. The flowable fill mixes were tested for plastic state characteristics, unconfined compressive strength, and confined compressive s...

Fuel, 2006

Grouting and Deep Mixing 2012, 2012

There are many challenges in relation to reusing closed landfill sites due to complex behaviour of creep, settlement and weak shear strength of decomposed wastes, and uncertainties to estimate their engineering properties. Deep mixing method is a ground improvement technique that can be used for chemical modification through solidifying the municipal solid wastes with lime, cement, fly ash or other binders. This paper presents compaction, permeability and shear strength mechanisms of the municipal solid wastes with or without chemical stabilisation using fly ash. The specimen preparation has been designed to simulate the treatment using the dry mixing method. Effect of curing time on properties of samples has also been examined. According to the experimental results and data taken from published literature, it is found that the chemical stabilisation can effectively decrease the permeation, whereas increase the compressibility and compressive strength of the municipal solid wastes.

Landfill liners are used for the efficient containment of waste materials generated from different sources. In the absence of impermeable natural soils, compacted mixtures of expansive soil and sand have found wide applications as landfill liners. It is to be noted that, in case, these materials are not locally available, the cost of the project increases manifold due to its import from elsewhere. Also, sand has become an expensive construction material due to its limited availability. With this in view, the present study attempts to explore a waste material such as fly ash as a substitute for sand. The major objective of this study is to maximize the use of fly ash for the said application. Different criteria for evaluating the suitability of material for landfill liner have been proposed in this study. However, further investigations are required with different source of fly ash and alternative material to generalize the findings.

Journal of Geochemical Exploration, 2006

In order to understand the long-term behavior of pollutants in the solidified/stabilized (S/S) Municipal Solid Waste Incineration (MSWI) fly ashes using cement, raw MSWI fly ashes, as well as aged and fresh S/S samples were studied. Materials were examined through chemical analyses, leaching and permeability tests, petrographical observations, X-ray diffraction, EDS-based TEM and SEM. Drastically high amounts of Cl− and Pb are leached from the solidified/stabilized MSWI fly ashes, due to both the presence of soluble minerals and a network of micro-cracks leading to a very low cohesion and an impermeability loss of the material. Beyond portlandite and calcite, the main major minerals identified in aged S/S MSWI fly ashes are hydrocalumite, ettringite and ordered silicate-hydrates mostly free of heavy metals. The ordered silicate-hydrates are missing in fresh samples. The large variety of heavy metal-bearing compounds is distributed between inherited stable phases (metallic alloys, sp...

Journal of Geotechnical and Geoenvironmental Engineering, 2007

Class F fly ash and bottom ash are the solid residue byproducts produced by coal-burning electric utilities. They are usually disposed of together as a waste in utility disposal sites with a typical disposal rate of 80% fly ash and 20% bottom ash. Direct use of these materials in construction projects consuming large volumes of materials, such as highway embankment construction, not only provides a promising solution to the disposal problem, but also an economic alternative to the use of traditional materials. Representative samples of class F fly and bottom ash were collected from two utility power plants in Indiana and tested for their mechanical properties ͑compaction, permeability, strength, stiffness, and compressibility͒. Three mixtures of fly and bottom ash with different mixture ratios ͑i.e., 50, 75, and 100% fly ash content by weight͒ were prepared for testing. Test results indicated that ash mixtures compare favorably with conventional granular materials.