Effect of strain rate on mobilised strength and thickness of curved shear bands

Einav, Itai; Randolph, Mark

doi:10.1680/geot.2006.56.7.501

Cited by 63 publications

(24 citation statements)

References 11 publications

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“…The drag coefficients C d is the intercept of C n and can be expressed as 0.6/sin θ for any impact angle, which was also suggested by Randolph and White (2012). It should be noted that the values N p,90 ¼ 11.61 and f a,0 ¼1.527 are close to the theoretical values of 11.9 (Randolph and Houlsby, 1984;Martin and Randolph, 2006) and 1.4 (Einav and Randolph, 2006;Randolph and White, 2012) for a fully rough pipe. The deduced values of the bearing factor N p and frictional coefficient f a based on CFD data are summarized in Table 7.…”

Section: Slurrysupporting

confidence: 67%

Impact forces of submarine landslides on offshore pipelines

Tian

2015

Ocean Engineering

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Section: Slurrysupporting

confidence: 67%

Impact forces of submarine landslides on offshore pipelines

Tian

2015

Ocean Engineering

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“…For the frictional resistance, R f2 was taken as 2R f1 from the previous reports (Einav and Randolph, 2006;Chow et al, 2014;Steiner et al, 2014). The predictions made the same assumptions based on the findings from the parametric studies, adopting _ γ ref ¼ 0.1 s À 1 and ξ a ¼0.35.…”

Section: Extended Bearing Resistance Methodsmentioning

confidence: 99%

Effect of strain rate and strain softening on embedment depth of a torpedo anchor in clay

2015

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a b s t r a c tTorpedo anchors (of diameter $ 1 m) are released from a height of 50-100 m from the seabed, achieving velocities up to 35 m/s at impacting the sediment. The strain rates induced in the surrounding soil by this dynamic installation is therefore significantly higher than those associated with installation of other offshore foundations and anchoring systems. The high strain rates enhance the mobilised undrained shear strength compared to that measured by in-situ penetrometer or laboratory tests. This paper reports the results from dynamic installation of a torpedo anchor in strain softening, rate dependent soft clays, quantifying the effects relative to results for ideal Tresca material. The three-dimensional dynamic large deformation finite element (LDFE) analyses were carried out using the coupled EulerianLagrangian approach. The simple elastic-perfectly plastic Tresca soil model was modified to allow strain softening and strain rate dependency of the shear strength. Parametric analyses were undertaken varying the strain rate parameter, the sensitivity and ductility of the soil, and the soil undrained shear strength. Overall, embedment depth for rate dependent, strain softening clays lay below that for ideal Tresca material. Increased strain rate dependency of the soil led to marked reduction in embedment depth, only partly compensated by brittleness. Key results have been presented in the form of design charts, fitted by simple expressions to estimate the embedment depth of a torpedo anchor.

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“…Graham et al (1983) proposed a simple equation that prescribes approximately a 5-20% increase in shear strength for each order of magnitude increase in the rate of shear strain. This effect can be expressed by the widely used equation (Einav & Randolph, 2006), and this value was adopted in the current study. For simplicity, the shear strength of a material can be assumed to be constant while integrating the constitutive equations during an individual time step of a non-linear finite-element analysis.…”

Section: Materials Behaviourmentioning

confidence: 99%

Dynamic analysis of a smooth penetrometer free-falling into uniform clay

Nazem¹,

Carter²,

Airey³

et al. 2012

Géotechnique

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The finite-element analysis of free-falling objects penetrating soil deposits is one of the most sophisticated and challenging problems in geomechanics. A robust numerical method will be described here for dealing with such complex and difficult problems. The approach is based on the arbitrary Lagrangian-Eulerian (ALE) method of analysis, the main features and challenges of which are described briefly in the paper. The ALE method is then employed to perform a parametric study of a perfectly smooth penetrometer free-falling into a uniform layer of clay, which deforms under undrained conditions. The effect of the mechanical properties of the clay soil on the penetration characteristics is presented, and an approximate, closed-form expression is derived for the dynamic penetration factor, N dp : Comparisons are made between the deduced values of N dp and published values of the conventional cone factor, N c , and comparisons are made with experimental data to validate the approach.KEYWORDS: numerical modelling; offshore engineering; shear strength; site investigation; soil/structure interaction L'analyse aux éléments finis d'objets en chute libre péné-trant dans des dépôts de sol est un des problèmes les plus sophistiqués et difficiles de la géomécanique. La présente communication décrit une méthode numérique robuste pour résoudre des problèmes aussi complexes et difficiles. Cette approche est basée sur la méthode d'analyse Lagrangien-Eulérien arbitraire (ALE), dont les principaux problèmes et caractéristiques sont décrits brièvement. On utilise ensuite la méthode ALE pour effectuer une étude paramétrique d'un pénétromètre parfaitement lisse tombant dans une couche d'argile uniforme, qui se déforme dans des conditions non drainées. On présente l'effet des propriétés mécaniques du sol d'argile sur les caractéris-tiques de pénétration, et on dérive une expression à forme fermée pour le facteur de pénétration dynamique N dp : On effectue des comparaisons entre les valeurs déduites de N dp et des valeurs publiées du facteur de cone N c , pour procéder ensuite à des comparaisons avec des données expérimentales pour valider cette approche.

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Effect of strain rate on mobilised strength and thickness of curved shear bands

Cited by 63 publications

References 11 publications

Impact forces of submarine landslides on offshore pipelines

Impact forces of submarine landslides on offshore pipelines

Effect of strain rate and strain softening on embedment depth of a torpedo anchor in clay

Dynamic analysis of a smooth penetrometer free-falling into uniform clay

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