ICE Virtual Library : Journals : Géotechnique

Géotechnique

ISSN: 0016-8505, E-ISSN: 1751-7656

Now publishing 12 issues per year in 2010.

Established for 60 years, Géotechnique is the world's premier geotechnics journal, publishing the research of the highest quality on all aspects of geotechnical engineering.

Géotechnique provides access to rigorously refereed, current, innovative and authoritative research and practical papers, across the fields of soil and rock mechanics, engineering geology and environmental geotechnics. The journal also publishes articles ahead of print to ensure you receive access to the latest research as soon as it is published. Ahead of print articles are fully citable using the DOI number, and subscribers can view the papers here.

2008 impact factor: 1.197 © Thomson Reuters Journal Citation Reports 2009

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Experimental analysis of the cyclic behaviour of kaolin at high temperature
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- Authors: C. Cekerevac; L. Laloui
- DOI: 10.1680/geot.7.00017
- This paper presents the results of an experimental study related to thermal effects on kaolin clay cyclic mobility. The thermal effects were identified by comparing the experimental results of cyclic triaxial tests performed at high temperature (908C) with results of the same type of test carried out at ambient temperature (228C). For the testing, a new temperature-controlled triaxial apparatus, developed by the authors, was employed. Experimental evidence shows that shear cycles on the heated samples induced smaller axial strain and pore-water pressure per cycle in comparison with the unheated samples. In addition, shear-induced pore-water pressure at large strains in the heated sample was slightly lower than in the unheated sample. In other words, the heated samples behaved as if they were denser, which is a result of thermal hardening. These results may be applied in geotechnical and earthquake engineering applications as a soil improvement technique.
- Available online: 10 March 2010
Strain path controlled shear tests on an analogue granular material
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- Authors: E. Ibraim; J. Lanier; D. Muir-Wood; G. Viggiani
- DOI: 10.1680/geot.8.P.100
- A series of strain controlled tests have been performed on a two-dimensional analogue granular material, composed of three different sizes of rods, in a special laboratory apparatus which permits full control of plane deformations, including rotation of principal axes. These tests have been designed and used to explore certain constitutive conjectures concerning the mechanical behaviour of granular materials. The results, within the accuracy of the apparatus, show that irrespective of the initial stress history of the material, proportional strain paths (if continued for long enough) lead to proportional stress states (asymptotic states). The asymptotic states appear to be independent of the fixed imposed rotation of principal strain axes and at these states coaxiality between the principal stress direction and the principal incremental strain direction seems to be reached. A stress dilatancy relationship between the imposed dilatancy and the corresponding asymptotic stress ratio has been identified.
- Available online: 25 January 2010
Creep, strength and other characteristics of Hawaiian volcanic soils
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- Authors: H. G. Brandes; D. D. Nakayama
- DOI: 10.1680/geot.8.P.117.3277
- Strength, creep and other properties of four volcanic soils from Hawaii were investigated under reconstituted triaxial conditions. The selected soils are of different geological origin and have contrasting index properties. Results from triaxial tests suggest that as clayey volcanic soils weather toward a siltier texture, their response to loading changes accordingly, with dilation at larger strains leading to an increase in strength. The frictional strength of two of these soils, a high-plasticity clay from Manoa Valley in Honolulu and a young ash soil from the Hilo area, does not correlate well with conventional empirical relations. In terms of creep behaviour, the response under constant stress conditions can be described, at least to a first order, with a simple rate process equation. A constant that is a measure of strain rate attenuation with time is observed to be stress level dependent at lower deviatoric stresses, but relatively constant at higher stress levels. This constant may be related to plasticity index, although such a correspondence is tenuous at best. Strength gain is observed in post-creep undrained tests, and is attributed in part to prior volume changes and in part to ageing. In terms of changes to the short-term failure envelope, the effect of a sustained creep phase of 100 days or longer is to shift the failure line upward, albeit at a constant angle.
- Available online: 25 January 2010
Stiffness characteristics of soluble mixtures
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- Authors: Q. H. Truong; Y. H. Eom; J. S. Lee
- DOI: 10.1680/geot.8.T.032
- Soils naturally contain grains of different minerals, which may be dissolved under chemical or physical processes. The dissolution leads to changes in the microstructure of the particulate media, such as an increase in local voids or permeability, which affects the strength and deformation of soils. This study focuses on the small strain stiffness characteristics of soluble mixtures, which consist of sand and salt particles at different volume fractions. Experiments were carried out in a conventional oedometer cell integrated with bender elements for the measurement of shear waves. Dissolutions of particles were implemented by saturating the mixtures at various confining stresses. Experimental results show that, after dissolution, the vertical strain and the void ratio increase, whereas the shear wave velocity decreases. The decrease of the velocity results from the void ratio increase and particle contact decrease. It is proven that specimens prepared from sand and salt particles are able to provide valuable insight into the macrostructural behaviour of soluble mixtures.
- Available online: 25 January 2010
Obituary: Olgierd Cecil Zienkiewicz, 1921–2009
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- Author: A. H. C. Chan
- DOI: 10.1680/geot.OB.8.009
- OBITUARY: Olgierd Cecil Zienkiewicz, 1921–2009
- Available online: 25 January 2010
Kinematics and rheology of a major landslide based on signal analysis
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- Authors: S. I. Pytharouli; S. C. Stiros
- DOI: 10.1680/geot.8.P.049
- A detailed geodetic record, which is over 23 years old and describes the kinematics of the Mandria (or Left Bank Upstream) landslide – a major deep-seated landslide close to the Polyphyton dam, Greece – was analysed on the basis of advanced signal analysis techniques without any geotechnical constraints. It was found that all points share the same pattern of displacement, which characterises both short and longer records. The overall behaviour of the landslide can be described as viscoelastic and viscous or elastoviscous, with multi-annual periodic effects superimposed on the creep, as the results of spectral analysis indicate. The landslide seems insensitive to seasonal variations of precipitation and to annual fluctuations of the reservoir level, although the first filling of the reservoir is likely to have had an important role in its movement. There is a lack of subsurface information, but the available data indicate that the landslide corresponds to a rigid mass dominated by brittle behaviour and internal shearing, with its kinematics controlled by thin mylonitic layers along low- and high-angle faults.
- Available online: 07 January 2010
A plasticity model for predicting the vertical and lateral behaviour of pipelines in clay soils
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- Authors: M. S. Hodder; M. J. Cassidy
- DOI: 10.1680/geot.8.P.055
- A complete theoretical model for predicting the undrained behaviour of a rigid pipe in clay soils when subjected to combined vertical and horizontal loading is described. Physical modelling of a pipe on soft, lightly overconsolidated kaolin clay was conducted, with the experimental test programme specifically designed to establish the model parameters. The testing was conducted within the University of Western Australia’s geotechnical drum centrifuge using an element of pipe 10 mm in diameter and 50 mm long, at an acceleration of 50 times the Earth’s gravity. The model presented is expressed by the force resultants on the pipe and the corresponding displacements and allows predictions of response to be made for various vertical and horizontal load or displacement combinations. However, it is limited to monotonic loading and does not account for the influence of berms created by repetitive large lateral displacements. The model is verified in this paper by retrospectively simulating a selection of combined loading tests and comparing the output with the experimentally recorded results.
- Available online: 07 January 2010
Discussion: Undrained monotonic and cyclic simple shear behaviour of carbonate sand
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- Authors: Wang Fu-qiang; D. Porcino; G. Caridi; V. N. Ghionna
- DOI: 10.1680/geot.8.D.017
- Discussion of Porcino et al. (2008) Undrained monotonic and cyclic simple shear behaviour of carbonate sand. Géotechnique 58(8): 635–644.
- Available online: 22 December 2009
Discussion: Calibrations of a high-suction tensiometer
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- Authors: E. C. Leong; H. Rahardjo; L. He; S. D. N. Lourenço; D. Gallipoli; D. G. Toll; C. E. Augarde; F. D. Evans; G. M. Medero
- DOI: 10.1680/geot.8.D.019
- Discussion of Lourenço et al. (2008) Calibrations of a high-suction tensiometer. Géotechnique 58(8): 659–668.
- Available online: 22 December 2009
Discussion: Undrained monotonic and cyclic simple shear behaviour of carbonate sand
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- Authors: S. López-Querol; D. Porcino; G. Caridi; V. N. Ghionna
- DOI: 10.1680/geot.8.D.021
- Discussion of Porcino et al. (2008) Undrained monotonic and cyclic simple shear behaviour of carbonate sand. Géotechnique 58(8): 635–644.
- Available online: 22 December 2009
Deep-penetrating spudcan foundations on layered clays: centrifuge tests
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- Authors: M. S. Hossain; M. F. Randolph
- DOI: 10.1680/geot.8.P.039
- Installation of independent-legged jack-up rigs in sea-bed sediments where a strong layer overlays weaker soil can lead to catastrophic ‘punch-through’, with potential leg buckling or toppling of the unit. Although approximate methods of analysis exist for estimating the penetration resistance, these do not account for the distortion of the upper layer as it punches through into the lower layer and there has been only limited visual depiction of the failure mechanism that occurs for the case of strong clay overlying weaker soil. This paper reports results of centrifuge model tests undertaken to provide insight into spudcan foundation behaviour during undrained vertical penetration through a stronger clay layer into weaker material, varying the strength ratio between lower and upper soil layers, the thickness of the upper layer relative to the spudcan diameter and the strength gradient of the lower layer. The model tests included half-spudcan tests against a transparent window, allowing the soil flow to be captured continuously by a digital camera and subsequently quantified through particle image velocimetry (PIV) analysis, and separate full-spudcan tests to measure the penetration resistance. Four interesting aspects of the soil flow mechanisms were identified: (a) vertically downwards motion of the soil and consequent deformation of the layer interface; (b) trapping of the stronger material beneath the spudcan, with this material being carried down into the underlying soft layer; (c) delayed back-flow of soil around the spudcan into the cavity formed above the spudcan; (d) eventual localised flow around the embedded spudcan. The effect of normalised layer soil properties and geometry on the soil flow mechanisms and the form of the penetration resistance profile is discussed in the context of the likelihood and severity of punchthrough failure. Typical critical failure modes involved punching shear, with clear shear planes in the shape of a truncated cone forming in the upper layer below the spudcan. Potential punch-through, with a peak in penetration resistance followed by some reduction, occurred for almost all cases investigated. The reduction in resistance became more severe as the strength ratio of the underlying layer to the upper layer reduced, and also as the upper layer thickness increased. The failure modes assumed by the currently available recommended practices are not consistent with those observed from the study, suggesting a more rational approach is needed.
- Available online: 22 December 2009
Deep-penetrating spudcan foundations on layered clays: numerical analysis
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- Authors: M. S. Hossain; M. F. Randolph
- DOI: 10.1680/geot.8.P.040
- This paper presents results of large deformation finite element (LDFE) analyses that investigate the penetration response of deep-penetrating spudcan foundations in stratified soil comprising a strong clay layer overlying weaker clay. Such strength profiles give rise to potential punchthrough failure, with a local maximum penetration resistance followed by some reduction. The paper is a companion paper to one that presents results from centrifuge model tests of the same problem, with the overall aim being to investigate the potential for punch-through failure and its severity, as a basis for improving design methods for evaluating spudcan penetration. The LDFE analyses have simulated continuous penetration of smooth and rough spudcan foundations from the sea-bed surface. A detailed parametric study has been undertaken, exploring the relevant range of layer thickness (relative to the spudcan diameter), strength ratios and spudcan base roughness. The results have been validated against previously published results and the centrifuge test data presented in a companion paper. Excellent agreement was obtained between the results from LDFE analyses and centrifuge tests. As the ratio of the shear strength of the bottom layer to that of the top layer decreased, upwards soil flow around the spudcan shoulder became less pronounced and the failure mechanism was dominated by a steep-sided plug of soil from the top layer being forced deep into the lower layer. The potential for severe punch-through was demonstrated by a significant reduction in the resistance profile as the spudcan approached the interface between the two layers. A preliminary design chart is proposed to estimate the cavity depth above the penetrating spudcan, which was significantly greater than that for a single layer clay. The penetration responses have been presented in terms of profiles of normalised net bearing pressure for a range of layer geometries and soil properties. Potential punchthrough occurred for all cases where the strength ratio was less than or equal to 0.6, with the reduction in resistance being greater the lower the strength ratio of the underlying layer to the upper layer, and the thicker the upper layer, but reducing as the strength gradient in the lower layer increased. The current approach suggested in offshore design guidelines is shown to underestimate the penetration resistance significantly, in most cases, and give poor estimates of the likelihood and severity of spudcan punch-through.
- Available online: 22 December 2009
Smear zone identification and soil properties around stone columns constructed in-flight in centrifuge model tests
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- Authors: T. M. Weber; M. Plötze; J. Laue; G. Peschke; S. M. Springman
- DOI: 10.1680/geot.8.P.098
- Stone columns are primarily used for the purpose of ground improvement in fine grained soils in order to reduce settlements and the risk of bearing failure. They are also designed to improve the drainage conditions in the ground and to accelerate the consolidation processes within the clay. However, smear and disturbing effects caused during the construction of stone columns result in degradation of consolidation performance in comparison with the theoretically ideal conditions. Model stone columns are constructed in-flight under 50 times gravity in centrifuge tests and the soil micro-structure in the vicinity of these columns is investigated by applying different methods, including environmental scanning electron microscopy and mercury intrusion porosimetry. The results of these tests confirm that smear and disturbance occur owing to stone column installation and the region influenced can be divided into three sections: a penetration zone (1) where the sand particles are squeezed through the clay; a smear zone (2) where the soil particles have experienced a significant reorientation; and a densification zone (3) where the structure of the clay does not appear to change, but compaction of the clay is measurable. The extremes of the disturbed zone around model stone columns are determined to extend to about 2.5 times the column radius.
- Available online: 22 December 2009
Effect of relative density and confining pressure on Poisson ratio from bender and extender elements tests
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- Authors: J. Kumar; B. N. Madhusudhan
- DOI: 10.1680/geot.9.T.003
- By using the bender and extender elements tests, together with measurements of the travel times of shear (S) and primary (P) waves, the variation of Poisson ratio (ν) was determined for dry sands with respect to changes in relative densities and effective confining pressures (σ₃). The tests were performed for three different ranges of particle sizes. The magnitude of the Poisson ratio decreases invariably with an increase in both the relative density and the effective confining pressure. The effect of the confining pressure on the Poisson ratio was found to become relatively more significant for fine-grained sand as compared with the coarse-grained sand. For a given material, at a particular value of σ₃, the magnitude of the Poisson ratio decreases, almost in a linear fashion, with an increase in the value of maximum shear modulus (G_max). The two widely used correlations in literature, providing the relationships among G_max, void ratio (e) and effective confining pressure (σ₃), applicable for angular granular materials, were found to compare reasonably well with the present experimental data for the fine and medium-grained sands. However, for the coarse grained sand, these correlations tend to overestimate the values of G_max.
- Available online: 21 December 2009
Unstable behaviour of model Jamuna micaceous sand
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- Authors: D. Wanatowski; J. Chu; V. N. Georgiannou
- DOI: 10.1680/geot.8.D.022
- Discussion of Georgiannou (2008) Unstable behaviour of model Jamuna micaceous sand. Géotechnique 58(10): 825–829.
- Available online: 18 December 2009
Modelling realistic shape and particle inertia in DEM
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- Authors: J. Ferellec; G. McDowell
- DOI: 10.1680/geot.9.T.015
- The use of clumps of overlapping spheres in DEM can be used to represent realistic particle shapes. This Technical Note discusses a method that is simple and fast, and highlights the key parameters influencing particle resolution. However, the problem with overlapping mass is that the density is non-uniform, which leads to incorrect moments of inertia and therefore rotational resistance. This Technical Note addresses this issue, and proposes a simple method to reduce the error in the principal moments of inertia. The effect on a falling heap of ballast particles is shown; the method improves not only behaviour, but also computational time.
- Available online: 18 December 2009
Stress–dilatancy relation for Mohr–Coulomb soils following a non-associated flow rule
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- Authors: J. Zhang; R. Salgado
- DOI: 10.1680/geot.8.T.039
- Rowe’s stress–dilatancy relation for frictional (cohesionless) materials has been a cornerstone of soil mechanics. The original derivation of this relationship was based on incorrect energy minimisation considerations, but the relationship was proven later by De Josselin de Jong using friction laws, and has been confirmed by a large body of experimental results. In contrast, the validity of Rowe’s stress–dilatancy relation for cohesive-frictional materials, which has also been used, although not as extensively, was never verified. This paper shows that Rowe’s stress–dilatancy relation for Mohr–Coulomb soils (cohesive-frictional materials) is in fact incorrect. The paper also provides a correct stress–dilatancy relationship for non-associated Mohr–Coulomb soils that have both cohesive and frictional strength components. The derivation of the relationship for cohesive-frictional soils presented in this paper relies on use of the sawtooth model together with the application of the laws of friction.
- Available online: 15 December 2009

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