Re-examination of Undrained Strength at Atterberg Limits Water Contents

Nagaraj, H. B.; Sridharan, A.; Mallikarjuna, H. M.

doi:10.1007/s10706-011-9489-7

Cited by 60 publications

(30 citation statements)

References 38 publications

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“…Although usually quite sharp for a given material, undrained strength-liquidity index correlations can also vary widely between geomaterials since the strengths mobilised at the Casagrande LL and PL states are not unique (Haigh et al, 2013;Nagaraj et al, 2012;O'Kelly, 2013c). This is compounded by general difficulties in measuring and interpreting consistency limit values for organic soils (O'Kelly, 2013a(O'Kelly, , 2013b(O'Kelly, , 2014a(O'Kelly, , 2016bO'Kelly and Zhang, 2013).…”

Section: With Liquidity Indexmentioning

confidence: 99%

“…Undrained strength against water content correlations for municipal sludge and residue materials: (a) bilinear axes, (b) semi-logarithmic plot and (c) bilogarithmic plots content, with such relationships often incorporating measured LL and PL values in the calculations, with the main ones reviewed by O'Kelly (2013c). Many of them assume a 100-fold strength variation between the water content values corresponding to the LL and PL conditions, but as O'Kelly (2013c) emphasised, there is no theoretical basis for this, with the ratio of the strengths mobilised at the PL and LL conditions varying over a wide range when many different soils are considered (Haigh et al, 2013;Nagaraj et al, 2012;O'Kelly, 2013cO'Kelly, , 2015b. This is particularly true for organic soils, including the municipal water/wastewater sludge and residue materials under consideration in this paper, for which the ratio of the strengths mobilised at the PL and LL has been found to be significantly less than 100 (O'Kelly, 2013c(O'Kelly, , 2014a(O'Kelly, , 2014b(O'Kelly, , 2015b(O'Kelly, , 2016bZentar et al, 2009).…”

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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: With Liquidity Indexmentioning

confidence: 99%

mentioning

confidence: 99%

Geotechnics of municipal sludges and residues for landfilling

O’Kelly

2016

Geotechnical Research

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“…To accomplish this, a Table 1. Undrained shear strengths (s u ) at liquid limit (adapted from Kayabali andTufenkci, 2010 andNagaraj et al, 2012 bulk soil sample was mixed with fine sand and commercial powdered bentonite at varying drymass ratios. The final product of this procedure is 60 soil samples with liquid limits ranging from about 30 to 120, which covers the plasticity range of most soils on earth.…”

Section: Methodsmentioning

confidence: 99%

“…The variation of the s u with the water content has been well-documented in the geotechnical literature. A brief summary of such studies was provided by Nagaraj et al (2012).…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Undrained Shear Strength of Fine-Grained Soils in Consideration of Soil Plasticity

Kayabalı¹,

Aktürk²,

Fener³

et al. 2016

YRB

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Undrained shear strength (s u ) is one of the key geotechnical parameters for both natural and remolded soils. While it is basically a function of water content, it is also related to soil plasticity. There has been a long-lasting debate as to whether the s u at the plastic and liquid limits are constant and whether the ratio of the s u at the plastic limit to the s u at the liquid limit is mostly fixed to 100. While this view is embraced by a great majority of researchers, some proclaim that the range of both the s u at the plastic limit (PL) and the s u at the liquid limit (LL) is rather wide; therefore, constant values of the s u cannot be assigned for either the PL or the LL. Accordingly, the view that there is a constant ratio between the two shear strengths is invalid. The scope of this investigation is to reassess this problem using the laboratory vane shear test (VST) along with a new supplementary tool, the mud-press machine (MPM). Sixty remolded soil samples were employed as the study material. The variation of soil strength at both the plastic and liquid limit is investigated using the VST and MPM methods. While the VST method does not portray a distinctive relationship between the s u and the two Atterberg limits, the newly introduced MPM method clearly shows that there is a meaningful relationship between the extrusion force, which is considered akin to the undrained shear strength, at the Atterberg limits and the two consistency limits, particularly the liquid limit. Concerning the constant ratio between the two shear strengths, namely the one at the plastic limit to the one at the liquid limit, it was found that this ratio is a constant, but it increases with the increase in soil plasticity.Keywords: Undrained shear strength, soil plasticity, vane shear test, mud press method, remolded soils. ÖZ Drenajsız kesme dayanımı (s u ) doğal ve yoğrulmuş zeminlerin ikisi için

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“…3, the strength gain factor (R MW ) for the traditionally defined plastic range is generally significantly different (and more often than not substantially less) than the assumed 100-fold increase. Prakash (2005) and Nagaraj et al (2012) cautioned against assigning a fixed strength value at PL. As explained in Haigh et al (2013), the assumption of a 100-fold factor increase derives from the following passage in Schofield & Wroth (1968), who were examining the data of Skempton & Northey (1952) (shown in Fig.…”

Section: Strength-based Approachesmentioning

confidence: 99%

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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Re-examination of Undrained Strength at Atterberg Limits Water Contents

Cited by 60 publications

References 38 publications

Geotechnics of municipal sludges and residues for landfilling

Geotechnics of municipal sludges and residues for landfilling

Evaluation of Undrained Shear Strength of Fine-Grained Soils in Consideration of Soil Plasticity

Use of fall cones to determine Atterberg limits: a review

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