Measuring the plastic limit of fine soils: an experimental study

Sivakumar, V.; O’Kelly, Brendan C.; Henderson, Laura; Moorhead, Catherine; Chow, Shiao Huey

doi:10.1680/geng.14.00004

Cited by 37 publications

(34 citation statements)

References 15 publications

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“…using the 80 g 30°cone in accordance with BSI (1990a)), the plastic strength limit PL 100 (Haigh et al, 2013;Kyambadde and Stone, 2012;Sivakumar et al, 2015) and the undrained shear strength of intact and remoulded clay for different water contents within the plastic range (e.g. using the 80 g 30°(BSI, 1990a), 100 g 30°or 400 g 30°cones (Geonor, 2015)) and to determine sensitivity (i.e.…”

Section: Fall Cone Approachesmentioning

confidence: 99%

“…For typical inorganic soils (m = 0·1, where m is the rate dependence parameter) and cone penetration depths ranging from 5 to 15 mm, the 400 g 60°fall cone provides for strength determinations covering the range of 5-50 kPa (O'Kelly, 2016b). Using the concept presented by Sivakumar et al (2015), O'Kelly (2016b) suggested that a lighter 60°cone which incorporates a falling distance (i.e. before the cone tip contacts the test specimen surface) can be used to achieve the same effect.…”

Section: Fall Cone Approachesmentioning

confidence: 99%

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Geotechnics of municipal sludges and residues for landfilling

O’Kelly

2016

Geotechnical Research

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This paper presents a comprehensive review of reported field and laboratory investigations and theoretical work concerning the geotechnical behaviour/properties of water treatment residue (WTR), biosolids and sewage sludge materials, which are by-products of municipal water and wastewater treatment processes. After describing the backgrounds to the generation of these materials and various disposal options (with a focus on landfilling), including associated geotechnical issues, their physical, geotechnical index, compaction, undrained strength and effective-stress strength properties are described, including the effects of oxidation, biodegradation and viscous gellike pore fluid for biosolids/sewage sludge material. Characteristic compressibility, consolidation and permeability behaviour/properties are also presented for these materials and linked with microstructure and the chemicals added during the treatment processes. The paper then focuses on various geotechnical issues pertinent to landfill (monofill) disposal of these materials, including undrained strength requirements, design strength, on-site and laboratory strength measurements and water content-strength correlations. Since such correlations are material specific, with the geotechnical properties of biosolids, sewage sludge and WTR materials varying between water/wastewater treatment plants, they cannot be applied more widely with confidence. Alternative approaches to predicting undrained strength are described, including a power-law strength relationship with water content, which can be applied more generally. , 2008a). The type and amount of chemicals added depends on the nature of the source water, but primarily on its turbidity and hardness. The coagulants cause the colloidal particles present to aggregate into flocs (with the polyelectrolyte also acting as a binding agent to increase their inherent shear strength) that are more readily separated out by settling processes, removing not only the impurities but also the chemical additives. NotationThe residue so formed is categorised as aluminium sulfate (alum) or iron WTR material depending on the coagulant salt, with the former being the most widely used coagulant in the water treatment industry. Lime-softening sludge, composed of typically 80-95 wt% calcite (Raghu and Hsieh, 1986), is the result of softening hard water before its distribution as drinking water.Biosolids and sewage sludge materials are highly organic residue by-products of municipal waste water treatment, with the organic fraction originating principally from human faeces (primary sludge) and bacterial biomass (secondary sludge) and the inorganic fraction derived from materials such as soil, sediment and inorganic residuals (Haynes et al., 2009). According to the US Environmental Protection Agency (EPA) (2015), sewage sludge refers to the solids separated out during the treatment processes, whereas biosolids refers to treated sewage sludge material that meets regulatory pollutant-and pathogen-control requirements for land applica...

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Section: Fall Cone Approachesmentioning

confidence: 99%

Section: Fall Cone Approachesmentioning

confidence: 99%

Geotechnics of municipal sludges and residues for landfilling

O’Kelly

2016

Geotechnical Research

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“…Simply based on analysis of historical data, as the ratio of strengths at the PL and LL varies substantially between soils, these strength-based approaches can only coincidentally give correct PL values, actually measuring what might be termed the plastic strength limit (PL 100 ); that is the water content corresponding to s uFC ¼ 100 Â s uFC(LL) . Fall cone Belviso et al, 1985;Wasti, 1987;Harison, 1988;Feng, 2000Feng, , 2001Feng, , 2004Koumoto & Houlsby, 2001;Sharma & Bora, 2003;Lee & Freeman, 2009;Shimobe, 2010;Sivakumar et al, 2015), steady monotonic penetration (Stone & Phan, 1995;Stone & Kyambadde, 2007), fast-static loading (Sivakumar et al, 2009) and extrusion (Timár, 1974;Whyte, 1982;Medhat & Whyte, 1986;Kayabali & Tufenkci, 2010a, 2010bKayabali, 2011aKayabali, , 2011bKayabali, , 2012Kayabali et al, 2016) approaches for PL determination have all been suggested as alternatives to the standard thread-rolling approach. As mechanical tests, these strength-based approaches are seen by some researchers as means of achieving higher degrees of repeatability and reproducibility of results, although, to date, most fall-cone research has been conducted on well-behaved clay-rich soils that lie above the A-line on the standard plasticity chart.…”

Section: Strength-based Approachesmentioning

confidence: 99%

“…Having recognised the important distinction between the true PL and that measured by strength-based tests, the 'PL' determined by the fall-cone approach has been referred to as the 'plastic strength limit' (Haigh et al, 2013) PL 100 (Harison, 1988;Stone & Phan, 1995;Stone & Kyambadde, 2007;Kyambadde & Stone, 2012;Haigh et al, 2013;O'Kelly, 2013;Kyambadde et al, 2014;Sivakumar et al, 2015Sivakumar et al, , 2016, with the subscript 100 indicating that the defined strength is 100 times the strength mobilised for the fall-cone LL (s uFC(LL) ). This assumes that cones having identical apex angle and surface roughness values are used in identifying both LL FC and PL 100 , and, furthermore, that the strain-rate dependency of the soil remains the same (as considered in the next section).…”

Section: Other Factors Influencing Deduced Atterberg Limit Valuesmentioning

confidence: 99%

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Use of fall cones to determine Atterberg limits: a review

2018

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This paper reviews the percussion-cup liquid limit, thread-rolling plastic limit (PL) and various fall-cone and other approaches employed for consistency limit determinations on fine-grained soil, highlighting their use and misuse for soil classification purposes and in existing correlations. As the PL does not correspond to a unique value of remoulded undrained shear strength, there is no scientific reason why PL measurements obtained using the thread-rolling and shear-strength-based fall-cone or extrusion methods should coincide. Various correlations are established relating liquid limit values deduced using the percussion-cup and fall-cone approaches. The significance of differences in the strain-rate dependency on the mobilised fall-cone shear strength is reviewed. The paper concludes with recommendations on the standardisation of international codes and the wider use of the fall-cone approach for soft to medium-stiff clays in establishing the strength variability with changing water content and further index parameters.

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Classifying and characterising fine‐grained soils using fall cones

et al. 2018

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Soil classification tests (liquid and plastic limits) are the most common tests performed in geotechnical engineering practice. In 'data poor' regions that are also vulnerable to natural hazards, they are often the only information engineers have available to assign parameters for geotechnical modelling and assessment purposes. This paper presents a review of some key correlations that rely on these data and summarises some recent research findings regarding the relationship between liquid limits measured using the Casagrande cup and fall-cone approaches, including the effect of different base hardness for the Casagrande cup device.

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Measuring the plastic limit of fine soils: an experimental study

Cited by 37 publications

References 15 publications

Geotechnics of municipal sludges and residues for landfilling

Geotechnics of municipal sludges and residues for landfilling

Use of fall cones to determine Atterberg limits: a review

Classifying and characterising fine‐grained soils using fall cones

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