In Situ Testing in Geomechanics

Schnaid, Fernando

doi:10.1201/9781482266054

Cited by 66 publications

(66 citation statements)

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“…Schnaid (2009) and Robertson (2009) proposed similar relationships but with slightly different exponents for Q tn . The ratio G o /q t is essentially a small-strain rigidity index (I G ), since it defines stiffness to strength ratio, where G o is the small-strain stiffness and q t is a measure of soil strength.…”

Section: Proposed Modified Sbtn Chartsmentioning

confidence: 72%

“…Robertson (2015) had suggested that K G is essentially a normalized rigidity index, since it normalizes the small-strain rigidity index (G o /q t ) with in situ soil state reflected by Q tn . The works by Eslaamizaad and Robertson (1996), Schnaid (2009), andMoss (2011) were focused primarily on coarse-grained soils. Robertson (2009) suggested that the small-strain rigidity index (I G ) can be extended to include fine-grained soils and should be defined based on net cone resistance q n , since q n is a more correct measure of soil strength, to be…”

Section: Proposed Modified Sbtn Chartsmentioning

confidence: 99%

“…Eslaamizaad and Robertson (1996) and Schnaid (2009) suggested that the SCPT can be helpful to identify soils with microstructure based on a link between G o /q t and Q tn , since both aging and bonding tend to increase the small-strain stiffness (G o ) significantly more than they increase the large-strain strength of a soil (reflected in both q t and Q tn ). Hence, for a given soil, age and bonding both tend to increase G o more than the larger strain cone resistance (q t ), all other factors (in situ stress state, etc.)…”

Section: Proposed Modified Sbtn Chartsmentioning

confidence: 99%

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Cone penetration test (CPT)-based soil behaviour type (SBT) classification system — an update

Robertson¹

2016

Can. Geotech. J.

315

212

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A soil classification system is used to group soils according to shared qualities or characteristics based on simple cost-effective tests. The most common soil classification systems used in geotechnical engineering are based on physical (textural) characteristics such as grain size and plasticity. Ideally, geotechnical engineers would also like to classify soils based on behaviour characteristics that have a strong link to fundamental in situ behaviour. However, existing textural-based classification systems have a weak link to in situ behaviour, since they are measured on disturbed and remolded samples. The cone penetration test (CPT) has been gaining in popularity for site investigations due to the cost-effective, rapid, continuous, and reliable measurements. The most common CPT-based classification systems are based on behaviour characteristics and are often referred to as a soil behaviour type (SBT) classification. However, some confusion exists, since most CPT-based SBT classification systems use textural-based descriptions, such as sand and clay. This paper presents an update of popular CPT-based SBT classification systems to use behaviour-based descriptions. The update includes a method to identify the existence of microstructure in soils, and examples are used to illustrate the advantages and limitations of such a system.Key words: cone penetration test (CPT), soil classification, microstructure, case histories.Résumé : Un système de classification des sols est utilisé pour grouper des sols selon les qualités partagées ou les caractéristiques basées sur des essais efficaces peu coûteux. Les systèmes de classification de sol les plus courants utilisés en génie géotechnique sont basés sur des caractéristiques physiques (textures) tels que la taille des grains et la plasticité. Idéalement, les ingénieurs géotechniques tiennent également à classer les sols en fonction des caractéristiques comportementales qui ont un lien étroit aux comportements fondamentaux in situ. Cependant, les systèmes existants de classification basés sur la texture ont un maillon faible au comportement in situ, car ils sont mesurés sur des échantillons perturbés et remaniés. Les essais faits au moyen de pénétration au cône (« cone penetration test » CPT) ont gagné en popularité pour les études de sites en raison des mesures rentables, rapides, continues et fiables. Les systèmes de classification basée sur le CPT les plus courants sont basés sur les caractéristiques du comportement et sont souvent appelés une classification de type de comportement de sol (« soil behaviour type » SBT). Toutefois, une certaine confusion existe puisque la plupart de systèmes de classification SBT basés sur le CPT utilisent des descriptions axées sur la texture, comme le sable et l'argile. Cet article présente une mise à jour des systèmes populaires de classification SBT basés sur le CPT, afin d'utiliser les descriptions basées sur le comportement. La mise à jour inclut une méthode pour identifier l'existence de microstructures dans les sols et ...

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Section: Proposed Modified Sbtn Chartsmentioning

confidence: 72%

Section: Proposed Modified Sbtn Chartsmentioning

confidence: 99%

Section: Proposed Modified Sbtn Chartsmentioning

confidence: 99%

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Cone penetration test (CPT)-based soil behaviour type (SBT) classification system — an update

Robertson¹

2016

Can. Geotech. J.

315

212

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“…In the present study, the coefficients of consolidation were measured in conventional oedometer consolidation tests and compared to values obtained in piezocone dissipation tests. The horizontal coefficients of consolidation were estimated from the dispersion of excess pore-pressures in the piezocone tests and defined according to Houlsby and Teh's method (1988) and the standard procedures proposed in the literature (Lunne et al, 1997;Schnaid, 2009).…”

Section: The C V Coefficientmentioning

confidence: 99%

Laboratory Parameters of a Soft Soil Deposit in Macaé, Brazil

Póvoa¹,

Nascimento²,

Maia³

2018

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Abstract. This article presents the geotechnical parameters from a laboratory investigation of a Quaternary sedimentary deposit located in a low-lying area of Macaé, Rio de Janeiro (RJ), Brazil, and, when possible, compares these parameters with those from field tests and other Brazilian studies on soft soils. The deposit is described in terms of its geological origin, physical, chemical and mineralogical characterization, compressibility, consolidation and strength. To that end, a series of laboratory tests were performed, including physical, chemical and mineralogical characterization, conventional and special consolidation, and triaxial tests. The results obtained made it possible to determine the geotechnical properties considered essential for improving knowledge on the behavior of this layer. Differences between laboratory and field parameters were observed, and the geotechnical characteristics of the Macaé deposits were found to be similar to those of other Brazilian soft soils.

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“…The effect of structure on undrained shear strength is most frequently presented with a sensitivity index. This index may also be determined from CPTU with the function (Lunne et al 1997, Schnaid 2009, Robertson 2009):…”

Section: Shear Strength Parametersmentioning

confidence: 99%

Geotechnical Parameters of Alluvial Soils from in-situ Tests

Młynarek

Stefaniak

Wierzbicki

2012

Archives of Hydro-Engineering and Environmental Mechanics

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The article concentrates on the identification of geotechnical parameters of alluvial soil represented by silts found near Poznań and Elbląg. Strength and deformation parameters of the subsoil tested were identified by the CPTU (static penetration) and SDMT (dilatometric) methods, as well as by the vane test (VT). Geotechnical parameters of the subsoil were analysed with a view to using the soil as an earth construction material and as a foundation for buildings constructed on the grounds tested. The article includes an analysis of the overconsolidation process of the soil tested and a formula for the identification of the overconsolidation ratio OCR. Equation 9 reflects the relation between the undrained shear strength and plasticity of the silts analyzed and the OCR value. The analysis resulted in the determination of the N kt coefficient, which might be used to identify the undrained shear strength of both sediments tested. On the basis of a detailed analysis of changes in terms of the constrained oedometric modulus M 0 , the relations between the said modulus, the liquidity index and the OCR value were identified. Mayne's formula (1995) was used to determine the M 0 modulus from the CPTU test. The usefullness of the sediments found near Poznań as an earth construction material was analysed after their structure had been destroyed and compacted with a Proctor apparatus. In cases of samples characterised by different water content and soil particle density, the analysis of changes in terms of cohesion and the internal friction angle proved that these parameters are influenced by the soil phase composition (Fig. 18 and 19). On the basis of the tests, it was concluded that the most desirable shear strength parameters are achieved when the silt is compacted below the optimum water content.

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In Situ Testing in Geomechanics

Cited by 66 publications

References 0 publications

Cone penetration test (CPT)-based soil behaviour type (SBT) classification system — an update

Cone penetration test (CPT)-based soil behaviour type (SBT) classification system — an update

Laboratory Parameters of a Soft Soil Deposit in Macaé, Brazil

Geotechnical Parameters of Alluvial Soils from in-situ Tests

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