Documents disponibles écrits par cet auteur

Centrifuge modeling of prefabricated vertical drains for liquefaction remediation / Rachelle Howell in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 3 (Mars 2012) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 3 (Mars 2012) . - pp. 262-271 Titre : Centrifuge modeling of prefabricated vertical drains for liquefaction remediation Type de document : texte imprimé Auteurs : Rachelle Howell, Auteur ; Ellen M. Rathje, Auteur ; Ronnie Kamai, Auteur Année de publication : 2012 Article en page(s) : pp. 262-271 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Liquefaction  Soil  improvement  Prefabricated  vertical  drains  Centrifuge  modeling Résumé : Drainage methods for liquefaction remediation have been in use since the 1970s and have traditionally included stone columns, gravel drains, and more recently prefabricated vertical drains. This paper presents the results from a dynamic centrifuge test designed to evaluate the performance of a liquefiable site treated with prefabricated vertical drains. The centrifuge model consisted of gently sloping, untreated and treated liquefiable soil deposits overlain by a clay crust. The model was subjected to multiple shaking events that included both recorded earthquake acceleration-time histories and sinusoidal input motions. Comparisons of deformations and excess pore water pressures in the untreated and treated areas showed that drains were effective in expediting the dissipation of excess pore water pressures and reducing deformations. However, depending on the characteristics of the input ground motion, the peak excess pore pressures in the treated area were not always substantially smaller than in the untreated area. Nevertheless, the deformations in the treated area were consistently smaller, which illustrates that the peak excess pore pressure ratio may not be a good indicator of overall performance. On the basis of the data from the centrifuge test, a better indicator of overall performance may be the time spent at elevated excess pore water pressures, which related better to the magnitude of the resulting deformations. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v138/i3/p262_s1?isAuthorized=no [article] Centrifuge modeling of prefabricated vertical drains for liquefaction remediation [texte imprimé] / Rachelle Howell, Auteur ; Ellen M. Rathje, Auteur ; Ronnie Kamai, Auteur . - 2012 . - pp. 262-271. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 3 (Mars 2012) . - pp. 262-271 Mots-clés : Liquefaction  Soil  improvement  Prefabricated  vertical  drains  Centrifuge  modeling Résumé : Drainage methods for liquefaction remediation have been in use since the 1970s and have traditionally included stone columns, gravel drains, and more recently prefabricated vertical drains. This paper presents the results from a dynamic centrifuge test designed to evaluate the performance of a liquefiable site treated with prefabricated vertical drains. The centrifuge model consisted of gently sloping, untreated and treated liquefiable soil deposits overlain by a clay crust. The model was subjected to multiple shaking events that included both recorded earthquake acceleration-time histories and sinusoidal input motions. Comparisons of deformations and excess pore water pressures in the untreated and treated areas showed that drains were effective in expediting the dissipation of excess pore water pressures and reducing deformations. However, depending on the characteristics of the input ground motion, the peak excess pore pressures in the treated area were not always substantially smaller than in the untreated area. Nevertheless, the deformations in the treated area were consistently smaller, which illustrates that the peak excess pore pressure ratio may not be a good indicator of overall performance. On the basis of the data from the centrifuge test, a better indicator of overall performance may be the time spent at elevated excess pore water pressures, which related better to the magnitude of the resulting deformations. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v138/i3/p262_s1?isAuthorized=no

Empirical predictive models for earthquake-induced sliding displacements of slopes / Gokhan Saygili in Journal of geotechnical and geoenvironmental engineering, Vol. 134 N° 6 (Juin 2008) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N° 6 (Juin 2008) . - pp. 790–803 Titre : Empirical predictive models for earthquake-induced sliding displacements of slopes Type de document : texte imprimé Auteurs : Gokhan Saygili, Auteur ; Ellen M. Rathje, Auteur Année de publication : 2010 Article en page(s) : pp. 790–803 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Earthquakes  Landslides  Slope  stability  Probability  Seismic  effects Résumé : Earthquake-induced sliding displacement is the parameter most often used to assess the seismic stability of slopes. The expected displacement can be predicted as a function of the characteristics of the slope (yield acceleration) and the ground motion (e.g., peak ground acceleration), yet there is significant aleatory variability associated with the displacement prediction. Using multiple ground motion parameters to characterize the earthquake shaking can significantly reduce the variability in the prediction. Empirical predictive models for rigid block sliding displacements are developed using displacements calculated from over 2,000 acceleration–time histories and four values of yield acceleration. These empirical models consider various single ground motion parameters and vectors of ground motion parameters to predict the sliding displacement, with the goal of minimizing the standard deviation of the displacement prediction. The combination of peak ground acceleration and peak ground velocity is the two parameter vector that results in the smallest standard deviation in the displacement prediction, whereas the three parameter combination of peak ground acceleration, peak ground velocity, and Arias intensity further reduces the standard deviation. The developed displacement predictive models can be used in probabilistic seismic hazard analysis for sliding displacement or used as predictive tools for deterministic earthquake scenarios. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A6%2879 [...] [article] Empirical predictive models for earthquake-induced sliding displacements of slopes [texte imprimé] / Gokhan Saygili, Auteur ; Ellen M. Rathje, Auteur . - 2010 . - pp. 790–803. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N° 6 (Juin 2008) . - pp. 790–803 Mots-clés : Earthquakes  Landslides  Slope  stability  Probability  Seismic  effects Résumé : Earthquake-induced sliding displacement is the parameter most often used to assess the seismic stability of slopes. The expected displacement can be predicted as a function of the characteristics of the slope (yield acceleration) and the ground motion (e.g., peak ground acceleration), yet there is significant aleatory variability associated with the displacement prediction. Using multiple ground motion parameters to characterize the earthquake shaking can significantly reduce the variability in the prediction. Empirical predictive models for rigid block sliding displacements are developed using displacements calculated from over 2,000 acceleration–time histories and four values of yield acceleration. These empirical models consider various single ground motion parameters and vectors of ground motion parameters to predict the sliding displacement, with the goal of minimizing the standard deviation of the displacement prediction. The combination of peak ground acceleration and peak ground velocity is the two parameter vector that results in the smallest standard deviation in the displacement prediction, whereas the three parameter combination of peak ground acceleration, peak ground velocity, and Arias intensity further reduces the standard deviation. The developed displacement predictive models can be used in probabilistic seismic hazard analysis for sliding displacement or used as predictive tools for deterministic earthquake scenarios. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A6%2879 [...]

Estimating fully probabilistic seismic sliding displacements of slopes from a pseudoprobabilistic approach / Ellen M. Rathje in Journal of geotechnical and geoenvironmental engineering, Vol. 137 N° 3 (Mars 2011) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 3 (Mars 2011) . - pp. 208-217 Titre : Estimating fully probabilistic seismic sliding displacements of slopes from a pseudoprobabilistic approach Type de document : texte imprimé Auteurs : Ellen M. Rathje, Auteur ; Gokhan Saygili, Auteur Année de publication : 2011 Article en page(s) : pp. 208-217 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Probabilistic  Seismic  hazard  Assessment  Slope  displacement  Seismic  performance Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Permanent sliding displacements are used to evaluate the seismic stability of earth slopes, and current practice utilizes a pseudoprobabilistic approach to predict the expected sliding displacement. The pseudoprobabilistic approach specifies a design ground-motion level based on a probabilistic seismic hazard analysis and a specified hazard level (e.g., 2% probability of exceedance in 50 years), but the displacement is predicted deterministically based on the design ground-motion level. The fully probabilistic approach develops a hazard curve for sliding displacement, and it is used to assess the displacement of the slope for a given hazard level. Comparisons of the fully probabilistic and pseudoprobabilistic approaches indicate that the pseudoprobabilistic analysis provides nonconservative estimates of sliding displacement in most cases. This paper presents a modification to the pseudoprobabilistic approach that provides displacement values more consistent with the fully probabilistic approach. This modification involves specifying a displacement greater than the median, in order to take into account the uncertainty in the displacement prediction. The appropriate value of displacement above the median is a function of the ky/PGA value and the model used to predict the displacement. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i3/p208_s1?isAuthorized=no [article] Estimating fully probabilistic seismic sliding displacements of slopes from a pseudoprobabilistic approach [texte imprimé] / Ellen M. Rathje, Auteur ; Gokhan Saygili, Auteur . - 2011 . - pp. 208-217. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 3 (Mars 2011) . - pp. 208-217 Mots-clés : Probabilistic  Seismic  hazard  Assessment  Slope  displacement  Seismic  performance Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Permanent sliding displacements are used to evaluate the seismic stability of earth slopes, and current practice utilizes a pseudoprobabilistic approach to predict the expected sliding displacement. The pseudoprobabilistic approach specifies a design ground-motion level based on a probabilistic seismic hazard analysis and a specified hazard level (e.g., 2% probability of exceedance in 50 years), but the displacement is predicted deterministically based on the design ground-motion level. The fully probabilistic approach develops a hazard curve for sliding displacement, and it is used to assess the displacement of the slope for a given hazard level. Comparisons of the fully probabilistic and pseudoprobabilistic approaches indicate that the pseudoprobabilistic analysis provides nonconservative estimates of sliding displacement in most cases. This paper presents a modification to the pseudoprobabilistic approach that provides displacement values more consistent with the fully probabilistic approach. This modification involves specifying a displacement greater than the median, in order to take into account the uncertainty in the displacement prediction. The appropriate value of displacement above the median is a function of the ky/PGA value and the model used to predict the displacement. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i3/p208_s1?isAuthorized=no

Influence of input motion and site property variabilities on seismic site response analysis / Ellen M. Rathje in Journal of geotechnical and geoenvironmental engineering, Vol. 136 N° 4 (Avril 2010) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 4 (Avril 2010) . - pp. 607-619 Titre : Influence of input motion and site property variabilities on seismic site response analysis Type de document : texte imprimé Auteurs : Ellen M. Rathje, Auteur ; Albert R. Kottke, Auteur ; Whitney L. Trent, Auteur Année de publication : 2010 Article en page(s) : pp. 607-619 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Site  response  analysis  Input  motions  Soil  properties  Uncertainty Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Seismic site response analysis evaluates the influence of local soil conditions on earthquake ground shaking. There are multiple sources of potential uncertainty in this analysis; the most significant pertaining to the specification of the input motions and to the characterization of the soil properties. The influence of the selection of input ground motions on equivalent-linear site response analysis is evaluated through analyses performed with multiple suites of input motions selected to fit the same target acceleration response spectrum. The results indicate that a stable median surface response spectrum (i.e., within ±20% of any other suite) can be obtained with as few as five motions, if the motions fit the input target spectrum well. The stability of the median is improved to ±5 to 10% when 10 or 20 input motions are used. If the standard deviation of the surface response spectra is required, at least 10 motions (and preferably 20) are required to adequately model the standard deviation. The influence of soil characterization uncertainty is assessed through Monte Carlo simulations, where variations in the shear-wave velocity profile and nonlinear soil properties are considered. Modeling shear-wave velocity variability generally reduces the predicted median surface motions and amplification factors, most significantly at periods less than the site period. Modeling the variability in nonlinear properties has a similar, although slightly smaller, effect. Finally, including the variability in soil properties significantly increases the standard deviation of the amplification factors but has a lesser effect on the standard deviation of the surface motions. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v136/i4/p607_s1?isAuthorized=no [article] Influence of input motion and site property variabilities on seismic site response analysis [texte imprimé] / Ellen M. Rathje, Auteur ; Albert R. Kottke, Auteur ; Whitney L. Trent, Auteur . - 2010 . - pp. 607-619. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 4 (Avril 2010) . - pp. 607-619 Mots-clés : Site  response  analysis  Input  motions  Soil  properties  Uncertainty Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Seismic site response analysis evaluates the influence of local soil conditions on earthquake ground shaking. There are multiple sources of potential uncertainty in this analysis; the most significant pertaining to the specification of the input motions and to the characterization of the soil properties. The influence of the selection of input ground motions on equivalent-linear site response analysis is evaluated through analyses performed with multiple suites of input motions selected to fit the same target acceleration response spectrum. The results indicate that a stable median surface response spectrum (i.e., within ±20% of any other suite) can be obtained with as few as five motions, if the motions fit the input target spectrum well. The stability of the median is improved to ±5 to 10% when 10 or 20 input motions are used. If the standard deviation of the surface response spectra is required, at least 10 motions (and preferably 20) are required to adequately model the standard deviation. The influence of soil characterization uncertainty is assessed through Monte Carlo simulations, where variations in the shear-wave velocity profile and nonlinear soil properties are considered. Modeling shear-wave velocity variability generally reduces the predicted median surface motions and amplification factors, most significantly at periods less than the site period. Modeling the variability in nonlinear properties has a similar, although slightly smaller, effect. Finally, including the variability in soil properties significantly increases the standard deviation of the amplification factors but has a lesser effect on the standard deviation of the surface motions. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v136/i4/p607_s1?isAuthorized=no

Pore pressure generation of silty sands due to induced cyclic shear strains / Kenan Hazirbaba in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N° 12 (Décembre 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 12 (Décembre 2009) . - pp. 1892–1905 Titre : Pore pressure generation of silty sands due to induced cyclic shear strains Type de document : texte imprimé Auteurs : Kenan Hazirbaba, Auteur ; Ellen M. Rathje, Auteur Année de publication : 2010 Article en page(s) : pp. 1892–1905 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Pore  pressureSoil  liquefactionSiltsSandSoil  typeShear  testsStrainCyclic  tests Résumé : It is well established that the main mechanism for the occurrence of liquefaction under seismic loading conditions is the generation of excess pore water pressure. Most previous research efforts have focused on clean sands, yet sand deposits with fines are more commonly found in nature. Previous laboratory liquefaction studies on the effect of fines on liquefaction susceptibility have not yet reached a consensus. This research presents an investigation on the effect of fines content on excess pore water pressure generation in sands and silty sands. Multiple series of strain-controlled cyclic direct simple shear tests were performed to directly measure the excess pore water pressure generation of sands and silty sands at different strain levels. The soil specimens were tested under three different categories: (1) at a constant relative density; (2) at a constant sand skeleton void ratio; and (3) at a constant overall void ratio. The findings from this study were used to develop insight into the behavior of silty sands under undrained cyclic loading conditions. In general, beneficial effects of the fines were observed in the form of a decrease in excess pore water pressure and an increase in the threshold strain. However, pore water pressure appears to increase when enough fines are present to create a sand skeleton void ratio greater than the maximum void ratio of the clean sand. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000147 [article] Pore pressure generation of silty sands due to induced cyclic shear strains [texte imprimé] / Kenan Hazirbaba, Auteur ; Ellen M. Rathje, Auteur . - 2010 . - pp. 1892–1905. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 12 (Décembre 2009) . - pp. 1892–1905 Mots-clés : Pore  pressureSoil  liquefactionSiltsSandSoil  typeShear  testsStrainCyclic  tests Résumé : It is well established that the main mechanism for the occurrence of liquefaction under seismic loading conditions is the generation of excess pore water pressure. Most previous research efforts have focused on clean sands, yet sand deposits with fines are more commonly found in nature. Previous laboratory liquefaction studies on the effect of fines on liquefaction susceptibility have not yet reached a consensus. This research presents an investigation on the effect of fines content on excess pore water pressure generation in sands and silty sands. Multiple series of strain-controlled cyclic direct simple shear tests were performed to directly measure the excess pore water pressure generation of sands and silty sands at different strain levels. The soil specimens were tested under three different categories: (1) at a constant relative density; (2) at a constant sand skeleton void ratio; and (3) at a constant overall void ratio. The findings from this study were used to develop insight into the behavior of silty sands under undrained cyclic loading conditions. In general, beneficial effects of the fines were observed in the form of a decrease in excess pore water pressure and an increase in the threshold strain. However, pore water pressure appears to increase when enough fines are present to create a sand skeleton void ratio greater than the maximum void ratio of the clean sand. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000147

Probabilistic seismic hazard analysis for the sliding displacement of slopes / Ellen M. Rathje in Journal of geotechnical and geoenvironmental engineering, Vol. 134 N° 6 (Juin 2008) 

Permalink