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

Robertson, P. K.

doi:10.1139/cgj-2016-0044

Cited by 315 publications

(309 citation statements)

References 24 publications

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“…Piezocone data from reference sites (without GH), GH‐bearing sites, and calcareous cemented clay (after Robertson, ) plotted in: (a) Q tn − U 2 chart and (b) Q tn − Fr chart (Robertson, ). Data from GH‐bearing sites are represented by pink crosses where the GH content could not have been estimated and by different symbols and colors referring to estimates of GH content (i.e., S hmin , see legend).…”

Section: Resultsmentioning

confidence: 99%

Hydromechanical Properties of Gas Hydrate‐Bearing Fine Sediments From In Situ Testing

2018

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The hydromechanical properties of gas hydrate‐bearing sediment are key in assessing offshore geohazards and the resource potential of gas hydrates. For sandy materials, such properties were proved highly dependent on hydrate content (Sh) as well as on their distribution and morphology. Owing to difficulties in testing gas hydrate‐bearing clayey sediments, the impact of hydrates on the behavior of such materials remains poorly understood. Hence, to provide insight into the characterization of clayey sediments containing hydrate, this study relies on a unique database of in situ acoustic, piezocone, and pore pressure dissipation measurements collected in a high gas flux system offshore Nigeria. Compressional wave velocity measurements were used as means of both detecting and quantifying gas hydrate in marine sediments. The analysis of piezocone data in normalized soil classification charts suggested that contrary to hydrate‐bearing sands, the behavior of gas hydrate‐bearing clays tends to be contractive. Correlations of acoustic and geotechnical data have shown that the stiffness and strength tend to increase with increasing Sh. However, several sediment intervals sharing the same Sh have revealed different features of mechanical behavior; suggesting that stiffness and strength of gas hydrate‐bearing clays are influenced by the distribution/morphology of gas hydrate. Pore pressure dissipation data confirmed the contractive behavior of gas hydrate‐bearing clays and showed that at low hydrate content, the hydraulic diffusivity (Ch) decreases when Sh increases. However, for Sh exceeding 20%, it was shown that an increase of Ch with Sh could be linked to the presence of fractures in the hydrate‐sediment system.

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Section: Resultsmentioning

confidence: 99%

Hydromechanical Properties of Gas Hydrate‐Bearing Fine Sediments From In Situ Testing

2018

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“…According to Robertson [3] soils with K* g > 330 tend to have significant microstructure and the higher the value of K* g , the more microstructure is likely present. Hence, the soil with K* g > 330 can be classified as structured soil where traditional generalized CPT-based empirical correlations may have less reliability and where local modification may be needed [3]. Key classification parameters obtained in this study are shown in …”

Section: Soil Profile At the Test Sitementioning

confidence: 92%

“…The U 2 parameter represents the ratio of the generated pore pressure (the increase of pore pressure above static value) and the effective vertical pressure of soil. Robertson suggested a new Q tn -I G chart (Figure 3, right) to identify soils with microstructure, where I G is the small-strain rigidity index (I G = G o /(q t -σ v )) [3]. In this chart soils with microstructure are plotted on the right side of the K* g = 330 limit.…”

Section: Soil Profile At the Test Sitementioning

confidence: 99%

The Interpretation of CPTu, PMT, SPT and Cross-Hole Tests in Stiff Clay

Kavur

Dodigović

Jug

et al. 2019

IOP Conf. Ser.: Earth Environ. Sci.

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Abstract. The paper presents the comparison of results of CPTu, PMT, SPT and CH (crosshole) tests performed in stiff, heavily overconsolidated clay at a test location in Zagreb. This clay exhibits very high pore pressures generated during CPTu penetrations despite significant overconsolidation and relatively high values of shear strength and stiffness in its undisturbed, natural state. The clay is classified using the CPTu and CH test results in recently published soil classification charts based on the soil behaviour in (S)CPTu penetrations. The results of classifications indicate that the tested clay probably has a pronounced microstructure that is likely a consequence of the geological processes of cementation and aging. Effects of cementation and aging are manifested on very high shear wave velocities, as measured in cross-hole seismic tests, and consequently very high values of the small-strain modulus. The collapse of the soil structure at higher shear displacements is resulting in volume contractions and softening behaviour after reaching the peak shear strength. The study shows a relatively good agreement between CPTu, PMT and SPT parameters and adequate correlations have been established between the cone resistance (CPTu), limit pressure (PMT) and number of blows (SPT). The in situ state and parameters of strength, stiffness and compressibility of the clay tested are estimated based on the in situ test parameters as well as comparative laboratory test results obtained on undisturbed soil samples. Existing empirical correlations developed for the interpretation of CPTu test results are mainly from young and uncemented soils without microstructure and therefore, the results shown here are important for better understanding of the structured soil behaviour characteristics (stiffness, strength, and compressibility).

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“…In this article, results of three cone penetration tests executed at three construction sites in the city of Salzburg are discussed by means of existing soil behaviour type charts. Since the most familiar charts for practical engineering were developed for unstructured soils, Schneider et al [3] and Robertson [2] defined new correlations, which allow the detection of a possible microstructure. The following studies try to evaluate the presence of microstructural bonds in sedimentary deposits such as the Salzburger Seeton by using the mentioned correlations.…”

Section: Introductionmentioning

confidence: 99%

Mikrostruktur des Salzburger Seetons – Charakterisierung basierend auf Drucksondierungen

Oberhollenzer

Marte

Gasser

et al. 2019

Geomechanics and Tunnelling

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Piezocone penetration tests (CPTu tests) allow continuous measurements of the tip resistance, the sleeve friction and the pore water pressure over depth. Furthermore, they minimize the required time as well as costs for a soil characterization. Due to the difficulty related to undisturbed sample recovery of soils (i.e. of weak silty fine‐grained sediments) for laboratory testing, in situ investigations are becoming increasingly popular in geotechnical engineering. The article illustrates results of cone penetration tests, executed at three test sites in the city of Salzburg. It is shown that CPT‐based soil behaviour type charts according to Robertson lead to a realistic characterization of the underground conditions. The grain size distribution of the Salzburger Seeton varies between fine sand‐silt mixtures, which are found in the upper parts, to clayey silts in greater depths. According to CPT‐based soil behaviour type charts of Robertson clayey silts behave clay‐like contractive and are characterized by homogeneous properties with increasing depth. Qtn‐IG diagrams underline that the Salzburger Seeton with a high clay content presents a weak microstructure. On the other hand, the upper Seeton layers, which can be classified as silt‐sand mixtures and silty sands respectively, show a stronger bounding between the particles.

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

Cited by 315 publications

References 24 publications

Hydromechanical Properties of Gas Hydrate‐Bearing Fine Sediments From In Situ Testing

Hydromechanical Properties of Gas Hydrate‐Bearing Fine Sediments From In Situ Testing

The Interpretation of CPTu, PMT, SPT and Cross-Hole Tests in Stiff Clay

Mikrostruktur des Salzburger Seetons – Charakterisierung basierend auf Drucksondierungen

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