On Liquefaction Phenomena, by Professor A. Casagrande: Report of Lecture

Green, P. A.; Ferguson, Phoebe

doi:10.1680/geot.1971.21.3.197

Cited by 40 publications

(5 citation statements)

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“…In the study of the mechanical behaviour of sands with particular reference to the liquefaction phenomenon (e.g. Casagrande, 1971;Poulos et al, 1985;Verdugo & Ishihara, 1996;Yang, 2002), it has been well recognised that various aspects of the behaviour can be characterised in the framework of critical state soil mechanics, which defines a unique critical state locus in the void ratio-mean effective stress (i.e. e-p′) plane such that the locus serves as a boundary separating the initial states of sand into contractive and dilative regions (Schofield & Wroth, 1968;Been & Jefferies, 1985;Wood, 1990).…”

Section: Unified Characterisation Of Gmentioning

confidence: 99%

Shear wave velocity and stiffness of sand: the role of non-plastic fines

2016

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Current knowledge on the shear wave velocity (V s ) and associated stiffness (G 0 ) of sand is built mainly on the results of extensive laboratory studies on clean quartz sands. Often natural sands are not clean, but contain a certain amount of fines. The role of fines in altering the stiffness of sands is a matter of great concern, yet remains poorly understood. This paper presents an investigation into the problem through well-controlled laboratory experiments in conjunction with analysis and interpretation at the macro and micro scale. The laboratory experiments were conducted for a sequence of mixtures of clean quartz sand and crushed silica fines under saturated conditions, by the simultaneous use of the resonant column (RC) and bender element (BE) techniques. A broad range of states in terms of void ratio, confining stress and fines content was covered so as to obtain a comprehensive view on the effect of fines and the possible interplay with other factors. Both the RC and BE tests showed that G 0 tends to decrease continuously as the quantity of fines is increased and the reduction rates are similar; a similar stress dependence is also obtained for G 0 from both types of testing. Nevertheless, G 0 values obtained from BE tests are notably greater than those obtained from RC tests, and this effect of testing method is shown to be coupled with the sample reconstitution method. A new approach that allows unified characterisation of G 0 values for both clean sand and sand-fines mixtures is developed in a sound theoretical framework, thereby providing important insights into the various empirical correlations that involve G 0 (or V s ) in geotechnical engineering practice. A new micro-scale mechanism is also suggested for the observed effect of fines, which attributes the reduction of G 0 caused by fines to the decrease in the coordination number at an approximately constant void ratio.

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Section: Unified Characterisation Of Gmentioning

confidence: 99%

Shear wave velocity and stiffness of sand: the role of non-plastic fines

2016

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“…There has been abundant evidence that loose, saturated sand, when subjected to monotonic shearing under undrained conditions, will undergo a sudden loss of strength and a rapid development of deformation (e.g. Casagrande, 1971;Castro et al, 1982;Ishihara, 1993;Yang, 2002). This collapse behaviour, known as flow or static liquefaction, can result in catastrophic consequences for geotechnical applications.…”

Section: Introductionmentioning

confidence: 99%

Collapse of loose sand with the addition of fines: the role of particle shape

Yang¹,

Wei²

2012

Géotechnique

291

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This paper describes a fundamental study to explore the role of particle shape in the shear behaviour of mixtures of sand and fine particles (fines) through macro-scale and grain-scale laboratory experiments together with interpretations in the framework of critical state soil mechanics and conceptual micromechanics models. Two non-plastic fines of distinct shape (angular crushed silica fines and rounded glass beads) were added to two uniform quartz sands (Toyoura sand and Fujian sand) to produce four binary mixtures. Laboratory quantification of particle shape and size was conducted for both fines and sands, and a series of undrained triaxial tests was performed to investigate the overall response of the mixed soils at different percentages of fines. One of the significant findings is that the critical state friction angle of a mixed soil is affected not only by the shape of coarse particles but also by the shape of fine particles, and this shape effect is coupled with fines content. When a small amount of crushed silica fines was added to either Toyoura sand or Fujian sand, the critical state friction angle increased slightly with fines content; however, when a small amount of glass beads was added to either sand, the critical state friction angle decreased markedly with an increase in fines content. A new index, termed combined roundness, is proposed to account for the coupled effects of particle shape and fines content. The study also provides evidence showing that the undrained shear behaviour and collapsibility of a mixed soil are closely related to the shape of its constituent particles: a mixed soil containing rounded fines tends to exhibit higher susceptibility to collapse than a mixed soil containing angular fines of the same percentage, and this tendency will become more evident if the base sand is also composed of rounded particles. In addition, the study provides the first experimental evidence showing that the quasi-steady state marks a transition from a metastable to a stable microstructure. It is postulated that in a binary mixture composed of fine and coarse particles that are both rounded, the particles favour rolling, thus yielding a microstructure that is unstable, whereas in a binary mixture composed of fine and coarse particles that are both angular, the particles favour sliding rather than rolling, thus leading to a much more stable structure and response.

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“…As is well known in geotechnical literature, [60][61][62] phase transition takes place in loose granular media when the specimen is sheared under constant volume conditions (that is undrained conditions if the material is saturated). Static liquefaction is the term used to describe the phenomenon associated with the nullification of effective pressure.…”

Section: Model Discussionmentioning

confidence: 99%

Phase transition in monodisperse granular materials: How to model it by using a strain hardening visco‐elastic‐plastic constitutive relationship

Marveggio

Redaelli

Prisco

2022

Num Anal Meth Geomechanics

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During heating (loading characterised by a progressive increase in strain rate) and cooling (loading characterised by a progressive decrease in strain rate) numerical tests, performed by using Discrete Element codes, granular materials experience phase transition phenomena, named in this paper ‘dry liquefaction’ (when from solid the material starts behaving like a fluid) and ‘dry resolidification’ (freezing, when the material from fluid starts behaving like a solid). The aim of this paper consists in reproducing phase transition phenomena by using a strain hardening visco‐elastic‐plastic model based on the critical state concept and kinetic theories of granular gases. The authors demonstrate that crucial is the role of isotropic softening/hardening, which describes the size of the elastic domain and the capability of the solid skeleton of storing elastic energy according to permanent force chains. The main ingredients of the model are: (i) the additivity of quasi‐static and collisional stresses, (ii) the energy balance equation governing the evolution of the granular temperature, interpreted this latter as an additional internal variable for the system for the collisional contribution, (iii) the mixed isotropic and kinematic hardening characterising the quasi‐static incremental constitutive relationship. The model has been both calibrated and validated on Discrete Element Method (DEM) numerical results, obtained by testing dry assemblies of monodisperse spheres under true triaxial loading conditions.

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On Liquefaction Phenomena, by Professor A. Casagrande: Report of Lecture

Cited by 40 publications

References 0 publications

Shear wave velocity and stiffness of sand: the role of non-plastic fines

Shear wave velocity and stiffness of sand: the role of non-plastic fines

Collapse of loose sand with the addition of fines: the role of particle shape

Phase transition in monodisperse granular materials: How to model it by using a strain hardening visco‐elastic‐plastic constitutive relationship

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