Dépouillements

The bearing capacity of footings on granular soils. I, Numerical analysis / C. K. Lau in Géotechnique, Vol. 61 N° 8 (Août 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 8 (Août 2011) . - pp. 627–638 Titre : The bearing capacity of footings on granular soils. I, Numerical analysis Type de document : texte imprimé Auteurs : C. K. Lau, Auteur ; M. D. Bolton, Auteur Année de publication : 2011 Article en page(s) : pp. 627–638 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Stress  analysis  Bearing  capacity  Shear  strength  Footings/foundations  Plasticity  Numerical  modelling Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : The method of characteristics has been used to determine the bearing capacity of shallow foundations, in either plane-strain or axisymmetric condition. Most previous solutions for granular soils were based either on a straight (c, φ ) envelope or simply on a constant angle of shearing, φ . For granular soils, sec φ usually varies linearly with the logarithm of mean effective stress. A new method of calculation permits φ to vary throughout the stress field as an arbitrary (or empirical) function of stress. This method is verified for both plane-strain and axisymmetric conditions by forcing a variation in sec φ equivalent to generating a constant-cohesion envelope, for which solutions already exist. The variable- φ analysis is used to demonstrate the highly significant effect of stress variation around and beneath a footing. Finally, it is shown that an equivalent constant value φ m can be derived empirically, using the new solutions to identify an equivalent mean effective stress p m. However, only the variable- φ solution can simultaneously capture the bearing capacity and the geometry of the bearing mechanism. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.7.00206 [article] The bearing capacity of footings on granular soils. I, Numerical analysis [texte imprimé] / C. K. Lau, Auteur ; M. D. Bolton, Auteur . - 2011 . - pp. 627–638. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 8 (Août 2011) . - pp. 627–638 Mots-clés : Stress  analysis  Bearing  capacity  Shear  strength  Footings/foundations  Plasticity  Numerical  modelling Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : The method of characteristics has been used to determine the bearing capacity of shallow foundations, in either plane-strain or axisymmetric condition. Most previous solutions for granular soils were based either on a straight (c, φ ) envelope or simply on a constant angle of shearing, φ . For granular soils, sec φ usually varies linearly with the logarithm of mean effective stress. A new method of calculation permits φ to vary throughout the stress field as an arbitrary (or empirical) function of stress. This method is verified for both plane-strain and axisymmetric conditions by forcing a variation in sec φ equivalent to generating a constant-cohesion envelope, for which solutions already exist. The variable- φ analysis is used to demonstrate the highly significant effect of stress variation around and beneath a footing. Finally, it is shown that an equivalent constant value φ m can be derived empirically, using the new solutions to identify an equivalent mean effective stress p m. However, only the variable- φ solution can simultaneously capture the bearing capacity and the geometry of the bearing mechanism. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.7.00206

The bearing capacity of footings on granular soils. II, Experimental evidence / C. K. Lau in Géotechnique, Vol. 61 N° 8 (Août 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 8 (Août 2011) . - pp. 639–650 Titre : The bearing capacity of footings on granular soils. II, Experimental evidence Type de document : texte imprimé Auteurs : C. K. Lau, Auteur ; M. D. Bolton, Auteur Année de publication : 2011 Article en page(s) : pp. 639–650 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Footings/foundations  Centrifuge  modelling  Sands  Model  tests  Bearing  capacity  Silts Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Scale effects, especially stress-level effects, cause considerable confusion in the calculation of bearing capacity on granular soils. A companion paper describes a new method of calculation that explicitly allows for the variation of sec φ with mean effective stress p. This approach is validated here for the case of model circular footings on dense beds of silica sand and silica silt. The models were tested at 1g with surcharge to explore the N q behaviour, and in a centrifuge to determine self-weight effects for N γ . It is shown that triaxial φ values expressed as a function of the logarithm of p can be used to predict model bearing capacities within a deviation in φ of 2°. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.7.00207 [article] The bearing capacity of footings on granular soils. II, Experimental evidence [texte imprimé] / C. K. Lau, Auteur ; M. D. Bolton, Auteur . - 2011 . - pp. 639–650. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 8 (Août 2011) . - pp. 639–650 Mots-clés : Footings/foundations  Centrifuge  modelling  Sands  Model  tests  Bearing  capacity  Silts Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Scale effects, especially stress-level effects, cause considerable confusion in the calculation of bearing capacity on granular soils. A companion paper describes a new method of calculation that explicitly allows for the variation of sec φ with mean effective stress p. This approach is validated here for the case of model circular footings on dense beds of silica sand and silica silt. The models were tested at 1g with surcharge to explore the N q behaviour, and in a centrifuge to determine self-weight effects for N γ . It is shown that triaxial φ values expressed as a function of the logarithm of p can be used to predict model bearing capacities within a deviation in φ of 2°. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.7.00207

Effect of soil characteristics on relative values of piezocone, T-bar and ball penetration resistances / H. E. Low in Géotechnique, Vol. 61 N° 8 (Août 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 8 (Août 2011) . - pp. 651–664 Titre : Effect of soil characteristics on relative values of piezocone, T-bar and ball penetration resistances Type de document : texte imprimé Auteurs : H. E. Low, Auteur ; M. F. Randolph, Auteur ; T. Lunne, Auteur Année de publication : 2011 Article en page(s) : pp. 651–664 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Shear  strength  Clays  Site  investigation  In  situ  testing Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : It has been reported in the literature that net cone penetration resistance is normally higher than the penetration resistance measured using full-flow cylindrical (T-bar) or spherical (ball) penetrometers, and also that the ball penetration resistance is generally very close to the T-bar penetration resistance. In this paper, a worldwide high-quality database (three onshore sites and seven offshore sites) was used to identify soil characteristics that contribute to differences in the relative magnitudes of penetration resistance measured with cone, T-bar and ball penetrometers. For soils covered in this database, the ratio of T-bar to net cone penetration resistance (q T-bar/q net) lay between 0·75 and 1, decreasing with depth from near unity at shallow depths. For the four sites where ball penetrometer data were available, the ratio of ball to T-bar penetration resistance (q ball/q T-bar) was found to fluctuate around unity, with an average just greater than 1, but no distinguishable trend with depth. The measured q T-bar/q net and q ball/q net followed theoretical trends for the cone resistance to increase with rigidity index, G/s u, with the best quantitative agreement obtained using a rigidity index defined in terms of the small strain stiffness, G 0, as measured by in situ seismic cone tests. The resistance ratio also followed the theoretical trend predicted with certain assumptions for the effects of strength anisotropy. However, while q T-bar/q net and possibly q ball/q net appear to depend slightly on the liquidity index, liquid limit and plasticity index, the resistance ratios appeared independent of other soil parameters, including normalised in situ shear stress, sensitivity and yield stress ratio, for the soils covered in this study. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.018 [article] Effect of soil characteristics on relative values of piezocone, T-bar and ball penetration resistances [texte imprimé] / H. E. Low, Auteur ; M. F. Randolph, Auteur ; T. Lunne, Auteur . - 2011 . - pp. 651–664. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 8 (Août 2011) . - pp. 651–664 Mots-clés : Shear  strength  Clays  Site  investigation  In  situ  testing Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : It has been reported in the literature that net cone penetration resistance is normally higher than the penetration resistance measured using full-flow cylindrical (T-bar) or spherical (ball) penetrometers, and also that the ball penetration resistance is generally very close to the T-bar penetration resistance. In this paper, a worldwide high-quality database (three onshore sites and seven offshore sites) was used to identify soil characteristics that contribute to differences in the relative magnitudes of penetration resistance measured with cone, T-bar and ball penetrometers. For soils covered in this database, the ratio of T-bar to net cone penetration resistance (q T-bar/q net) lay between 0·75 and 1, decreasing with depth from near unity at shallow depths. For the four sites where ball penetrometer data were available, the ratio of ball to T-bar penetration resistance (q ball/q T-bar) was found to fluctuate around unity, with an average just greater than 1, but no distinguishable trend with depth. The measured q T-bar/q net and q ball/q net followed theoretical trends for the cone resistance to increase with rigidity index, G/s u, with the best quantitative agreement obtained using a rigidity index defined in terms of the small strain stiffness, G 0, as measured by in situ seismic cone tests. The resistance ratio also followed the theoretical trend predicted with certain assumptions for the effects of strength anisotropy. However, while q T-bar/q net and possibly q ball/q net appear to depend slightly on the liquidity index, liquid limit and plasticity index, the resistance ratios appeared independent of other soil parameters, including normalised in situ shear stress, sensitivity and yield stress ratio, for the soils covered in this study. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.018

Modelling the stress–deformation behaviour of municipal solid waste / V. Krase in Géotechnique, Vol. 61 N° 8 (Août 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 8 (Août 2011) . - pp. 665–675 Titre : Modelling the stress–deformation behaviour of municipal solid waste Type de document : texte imprimé Auteurs : V. Krase, Auteur ; S. Bente, Auteur ; U. Kowalsky, Auteur Année de publication : 2011 Article en page(s) : pp. 665–675 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Numerical  modelling  Creep  Constitutive  relations  Deformation  Landfills Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Conceptual modelling of municipal solid waste landfills is vital for prognosis of the long-term development and the assessment of risk potential. Landfills are considered as heterogeneous porous structures, in which flow and transport processes of gases and liquids are combined with local material degradation and mechanical deformation of the solid skeleton. This contribution deals with a constitutive model focusing on the mechanical deformation behaviour of the disposed waste dividing the solid material into two different fractions. The first fraction includes more grainy particles and has properties comparable with granular materials. The second fraction consists of more fibrous constituents having an important influence on the strength of the composite material. Stress–strain behaviour of the two fractions is modelled according to the theory of finite elasto-plasticity. Settlements generated by mechanical creep are also included in the model. The developed constitutive model is validated and calibrated on results from laboratory experiments applying genetic algorithms. Numerical analyses using the finite-element method show the capability of the presented approach. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.140 [article] Modelling the stress–deformation behaviour of municipal solid waste [texte imprimé] / V. Krase, Auteur ; S. Bente, Auteur ; U. Kowalsky, Auteur . - 2011 . - pp. 665–675. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 8 (Août 2011) . - pp. 665–675 Mots-clés : Numerical  modelling  Creep  Constitutive  relations  Deformation  Landfills Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Conceptual modelling of municipal solid waste landfills is vital for prognosis of the long-term development and the assessment of risk potential. Landfills are considered as heterogeneous porous structures, in which flow and transport processes of gases and liquids are combined with local material degradation and mechanical deformation of the solid skeleton. This contribution deals with a constitutive model focusing on the mechanical deformation behaviour of the disposed waste dividing the solid material into two different fractions. The first fraction includes more grainy particles and has properties comparable with granular materials. The second fraction consists of more fibrous constituents having an important influence on the strength of the composite material. Stress–strain behaviour of the two fractions is modelled according to the theory of finite elasto-plasticity. Settlements generated by mechanical creep are also included in the model. The developed constitutive model is validated and calibrated on results from laboratory experiments applying genetic algorithms. Numerical analyses using the finite-element method show the capability of the presented approach. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.140

Reliability-based design of spread foundations by Monte Carlo simulations / Y. Wang in Géotechnique, Vol. 61 N° 8 (Août 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 8 (Août 2011) . - pp. 677–685 Titre : Reliability-based design of spread foundations by Monte Carlo simulations Type de document : texte imprimé Auteurs : Y. Wang, Auteur Année de publication : 2011 Article en page(s) : pp. 677–685 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Limit  state  design/analysis  Footings/foundations  Statistical  analysis  Numerical  modelling Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : In this paper a general reliability-based design (RBD) approach for spread foundations is developed that addresses, explicitly and simultaneously, the ultimate limit state (ULS), serviceability limit state (SLS), reliability and economic requirements. The design process is formulated as an expanded reliability problem that is evaluated by a single run of Monte Carlo simulations (MCS). Design parameters (i.e. foundation width B, length L and depth D) are artificially treated as discrete uniform random variables, and the design process is considered as a process of finding failure probabilities for designs with various combinations of B, L and D (i.e. conditional probability p(Failure|B,L,D)) and comparing them with target probability of failure p T. Feasible designs are those with p(Failure|B,L,D) ≤ p T, and the feasible design with the minimum construction cost is selected as the final design. Equations are derived for this expanded reliability-based design (RBDE) approach and criteria are established for the minimum number of MCS samples to ensure a desired level of accuracy. The RBDE approach with MCS is illustrated through a design example of a square spread foundation with a fixed depth that has been used for the evaluation of Eurocode 7. The results are consistent with those from previous reliability analysis reported in the literature. In addition, the RBDE approach with MCS offers design engineers insights into how the expected performance level of spread foundations changes as B, L and D change, and it allows design engineers to adjust p T, without additional computational efforts, to cater for the needs of particular projects. It also provides design engineers with flexibility in modelling the uncertainties and selecting proper deterministic ULS and SLS calculation models. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.p.016 [article] Reliability-based design of spread foundations by Monte Carlo simulations [texte imprimé] / Y. Wang, Auteur . - 2011 . - pp. 677–685. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 8 (Août 2011) . - pp. 677–685 Mots-clés : Limit  state  design/analysis  Footings/foundations  Statistical  analysis  Numerical  modelling Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : In this paper a general reliability-based design (RBD) approach for spread foundations is developed that addresses, explicitly and simultaneously, the ultimate limit state (ULS), serviceability limit state (SLS), reliability and economic requirements. The design process is formulated as an expanded reliability problem that is evaluated by a single run of Monte Carlo simulations (MCS). Design parameters (i.e. foundation width B, length L and depth D) are artificially treated as discrete uniform random variables, and the design process is considered as a process of finding failure probabilities for designs with various combinations of B, L and D (i.e. conditional probability p(Failure|B,L,D)) and comparing them with target probability of failure p T. Feasible designs are those with p(Failure|B,L,D) ≤ p T, and the feasible design with the minimum construction cost is selected as the final design. Equations are derived for this expanded reliability-based design (RBDE) approach and criteria are established for the minimum number of MCS samples to ensure a desired level of accuracy. The RBDE approach with MCS is illustrated through a design example of a square spread foundation with a fixed depth that has been used for the evaluation of Eurocode 7. The results are consistent with those from previous reliability analysis reported in the literature. In addition, the RBDE approach with MCS offers design engineers insights into how the expected performance level of spread foundations changes as B, L and D change, and it allows design engineers to adjust p T, without additional computational efforts, to cater for the needs of particular projects. It also provides design engineers with flexibility in modelling the uncertainties and selecting proper deterministic ULS and SLS calculation models. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.p.016

Physical characteristics of dynamic vertical–horizontal-rocking response of surface foundations on cohesionless soils / Ronald Y. S. Pak in Géotechnique, Vol. 61 N° 8 (Août 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 8 (Août 2011) . - pp. 687–697 Titre : Physical characteristics of dynamic vertical–horizontal-rocking response of surface foundations on cohesionless soils Type de document : texte imprimé Auteurs : Ronald Y. S. Pak, Auteur ; J. C. Ashlock, Auteur ; S. Kurahashi, Auteur Année de publication : 2011 Article en page(s) : pp. 687–697 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Soil/structure  interaction  dynamics  Vibration  Centrifuge  modelling  Sands Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : A fundamental experimental research programme on the dynamic behaviour of surface foundations on sand in general planar motion and the use of centrifuge modelling in soil–structure interaction studies is presented. Pursued with the dual purpose of extending the conventional formulation of dynamic test programmes as well as generating a physical database with sufficient parametric variations of the key aspects, an extensive experimental study to explore the dynamic soil–structure interaction problem in the small-amplitude regime is described. Through a comparison of the generated data with those from sequential vertical-centric and horizontal load tests, a novel hybrid-mode test concept by way of eccentric excitations is substantiated in terms of its economy and efficiency in capturing the force–response characteristics of the system. Synthesised in the frequency domain for direct qualitative and quantitative insights, multiple forced-response records of the foundation models on sand subjected to random vertical, horizontal and rocking excitations are summarised. As an illustration of the engineering relevance of the experimental database, a critical evaluation of the commonly used homogeneous half-space dynamic foundation solution pertaining to cohesionless soils is also provided. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.072 [article] Physical characteristics of dynamic vertical–horizontal-rocking response of surface foundations on cohesionless soils [texte imprimé] / Ronald Y. S. Pak, Auteur ; J. C. Ashlock, Auteur ; S. Kurahashi, Auteur . - 2011 . - pp. 687–697. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 8 (Août 2011) . - pp. 687–697 Mots-clés : Soil/structure  interaction  dynamics  Vibration  Centrifuge  modelling  Sands Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : A fundamental experimental research programme on the dynamic behaviour of surface foundations on sand in general planar motion and the use of centrifuge modelling in soil–structure interaction studies is presented. Pursued with the dual purpose of extending the conventional formulation of dynamic test programmes as well as generating a physical database with sufficient parametric variations of the key aspects, an extensive experimental study to explore the dynamic soil–structure interaction problem in the small-amplitude regime is described. Through a comparison of the generated data with those from sequential vertical-centric and horizontal load tests, a novel hybrid-mode test concept by way of eccentric excitations is substantiated in terms of its economy and efficiency in capturing the force–response characteristics of the system. Synthesised in the frequency domain for direct qualitative and quantitative insights, multiple forced-response records of the foundation models on sand subjected to random vertical, horizontal and rocking excitations are summarised. As an illustration of the engineering relevance of the experimental database, a critical evaluation of the commonly used homogeneous half-space dynamic foundation solution pertaining to cohesionless soils is also provided. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.072

Estimating hydraulic conductivity from piezocone soundings / J. C. Chai in Géotechnique, Vol. 61 N° 8 (Août 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 8 (Août 2011) . - pp. 699–708 Titre : Estimating hydraulic conductivity from piezocone soundings Type de document : texte imprimé Auteurs : J. C. Chai, Auteur ; P. M. A. Agung, Auteur ; T. Hino, Auteur Année de publication : 2011 Article en page(s) : pp. 699–708 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Sands  Clays Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : A method for estimating the hydraulic conductivity of soils from piezocone penetration tests is suggested in this paper. By invoking Darcy's law over the finite time required for an increment of cone penetration, it is argued that there will be some water movement through the soil around the cone, albeit very small if the soil is very fine grained. Based on this argument, and noting the comprehensive test data collected previously by Elsworth & Lee, a bi-linear relation between the dimensionless piezocone sounding metric B q Q t and the dimensionless hydraulic conductivity index K D plotted on double logarithmic scales has been proposed for soils ranging from sands to clays. It is demonstrated that these revised relationships can be used to evaluate plausible values of hydraulic conductivity from piezocone sounding records taken at two different clay soil sites in Saga and Yokohama, Japan. The major significance of this work is in extending the range of application of the method first proposed by Elsworth & Lee for sands to almost all soil types. This was possible after appropriate modification of Elsworth and Lee's original method. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.p.009 [article] Estimating hydraulic conductivity from piezocone soundings [texte imprimé] / J. C. Chai, Auteur ; P. M. A. Agung, Auteur ; T. Hino, Auteur . - 2011 . - pp. 699–708. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 8 (Août 2011) . - pp. 699–708 Mots-clés : Sands  Clays Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : A method for estimating the hydraulic conductivity of soils from piezocone penetration tests is suggested in this paper. By invoking Darcy's law over the finite time required for an increment of cone penetration, it is argued that there will be some water movement through the soil around the cone, albeit very small if the soil is very fine grained. Based on this argument, and noting the comprehensive test data collected previously by Elsworth & Lee, a bi-linear relation between the dimensionless piezocone sounding metric B q Q t and the dimensionless hydraulic conductivity index K D plotted on double logarithmic scales has been proposed for soils ranging from sands to clays. It is demonstrated that these revised relationships can be used to evaluate plausible values of hydraulic conductivity from piezocone sounding records taken at two different clay soil sites in Saga and Yokohama, Japan. The major significance of this work is in extending the range of application of the method first proposed by Elsworth & Lee for sands to almost all soil types. This was possible after appropriate modification of Elsworth and Lee's original method. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.p.009

On the operating critical friction ratio in general stress states / M. Jefferies in Géotechnique, Vol. 61 N° 8 (Août 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 8 (Août 2011) . - pp. 709–713 Titre : On the operating critical friction ratio in general stress states Type de document : texte imprimé Auteurs : M. Jefferies, Auteur ; D. Shuttle, Auteur Année de publication : 2011 Article en page(s) : pp. 709–713 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Sands  Numerical  modelling  Constitutive  relations Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Stress dilatancy provides a fundamental flow rule for constitutive models and several variations on the framework have similar operational performance. However, regardless of idealisation adopted for stress dilatancy, the scaling coefficient evolves and only attains the critical friction ratio at large strain. The scaling coefficient also depends on the proportion of intermediate principal stress. Data on stress dilatancy in triaxial compression and plane strain are reviewed. Based on these data, a simple function is proposed for stress-dilatancy scaling using an operational friction ratio M i based on work-conjugate stress and strain invariants. The function is calibrated to soil properties measured in conventional drained triaxial tests (about three, suitably chosen, tests are needed in addition to those used to define the critical state locus) and predicts strength in plane strain to an accuracy of ∆η = ±0·03 at 80% confidence for the Brasted and Changi sands considered (i.e. about ± 3% of typical peak strength). The proposed function is suitable for any soil constitutive model that includes a critical state line and which invokes stress dilatancy. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.t.032 [article] On the operating critical friction ratio in general stress states [texte imprimé] / M. Jefferies, Auteur ; D. Shuttle, Auteur . - 2011 . - pp. 709–713. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 8 (Août 2011) . - pp. 709–713 Mots-clés : Sands  Numerical  modelling  Constitutive  relations Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Stress dilatancy provides a fundamental flow rule for constitutive models and several variations on the framework have similar operational performance. However, regardless of idealisation adopted for stress dilatancy, the scaling coefficient evolves and only attains the critical friction ratio at large strain. The scaling coefficient also depends on the proportion of intermediate principal stress. Data on stress dilatancy in triaxial compression and plane strain are reviewed. Based on these data, a simple function is proposed for stress-dilatancy scaling using an operational friction ratio M i based on work-conjugate stress and strain invariants. The function is calibrated to soil properties measured in conventional drained triaxial tests (about three, suitably chosen, tests are needed in addition to those used to define the critical state locus) and predicts strength in plane strain to an accuracy of ∆η = ±0·03 at 80% confidence for the Brasted and Changi sands considered (i.e. about ± 3% of typical peak strength). The proposed function is suitable for any soil constitutive model that includes a critical state line and which invokes stress dilatancy. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.t.032

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