Plastic Limit, Liquid Limit and Undrained Shear Strength of Soil—Reappraisal

Sharma, Binu; Bora, Padma K.

doi:10.1061/(asce)1090-0241(2003)129:8(774)

Cited by 137 publications

(72 citation statements)

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“…Further, it has been well documented that, compared with the much-reduced concave curvatures of logarithm undrained strength against water content relationships ( Figure 11(b)), such relationships are nearly linear when presented on a bilogarithmic plot (Koumoto and Houlsby, 2001;Sharma and Bora, 2003), especially for soils having wide water content ranges under investigation and also for organic soils (O'Kelly 2014a(O'Kelly , 2016bZentar et al 2009). For instance, referring to Table 2, the bi-logarithmic data plots for the sewage sludge 1 and alum WTR 1-6 materials in Figure 11(c) generally gave higher coefficient of determination (R 2 ) values compared with the semilogarithmic plots of the same data in Figure 11(b).…”

Section: With Water Contentmentioning

confidence: 91%

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 Water Contentmentioning

confidence: 91%

Geotechnics of municipal sludges and residues for landfilling

O’Kelly

2016

Geotechnical Research

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“…67 3 10 4 %/min during penetration of the freefalling 80 g-308 cone used in this study. Karlsson (1981), Wood (1985) and Sharma and Bora (2003) have reported experimentally derived K values, in order, of 0 . 80, 0 .…”

Section: Shear Strength Measurementmentioning

confidence: 99%

“…82 using 308 cones with remoulded fine-grained mineral soils. Note that these experimental K values were calibrated against miniature vane data (Wood, 1985) and unconfined TC data (Sharma and Bora, 2003), for which the strain rate was approximately four orders of magnitude lower than that of the fall cone. The failure mechanism involved general shearing as the free-falling cone displaced the soil out of the way before coming to a stationary position.…”

Section: Shear Strength Measurementmentioning

confidence: 99%

“…All of the literature that reported the characteristics of remoulded undrained shear strength over the plastic range, including Koumoto and Houlsby (2001), Sharma and Bora (2003), Skempton and Northey (1953) and Wood (1990), would appear to concern fine-grained mineral soils, with a dearth of knowledge regarding organic soils. These experimental data indicate that the log wlog s ur relationship is linear over the plastic range, apart from high-plasticity montmorillonite soils, which exhibit bilinear relationships near the LL condition, with this characteristic difference in behaviour attributed to diffuse double-layer held water Bora, 2003, 2005).…”

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confidence: 99%

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Characterisation and undrained strength of amorphous clay

O’Kelly

2014

Proceedings of the Institution of Civil Engineers - Geotechnica

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This paper presents the physiochemical properties and relationship of saturated remoulded undrained shear strength, s ur , against water content, w, for an amorphous organic clay, namely an alum water-treatment residue material derived from the production of potable water. The log w-log s ur relationship was found to be strongly linear, and extended well beyond the measured plastic range. The effects of microstructure, and the shearing modes, rates and specimen confinement, are reported, along with the correspondence between s ur measured in triaxial compression and that deduced from fall-cone and miniature vane tests. The mobilised strength exhibited high strain-rate dependence, increasing by ,30%/log _ å cycle increase. The bulk water-treatment residue material could be easily remoulded at water contents below the measured Casagrande plastic limit, indicating that the reported plastic range was notional and, furthermore, that the use of liquidity index as an indicator of the material's consistency is unreliable. The paper concludes by presenting a conceptual model that goes towards explaining the relatively high values of s ur mobilised for this material at extremely high water contents.

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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%

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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Plastic Limit, Liquid Limit and Undrained Shear Strength of Soil—Reappraisal

Cited by 137 publications

References 4 publications

Geotechnics of municipal sludges and residues for landfilling

Geotechnics of municipal sludges and residues for landfilling

Characterisation and undrained strength of amorphous clay

Use of fall cones to determine Atterberg limits: a review

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