Documents disponibles écrits par cet auteur

Measuring dielectric constant in highly conductive soils based on surface reflection coefficients / Renpeng Chen 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. 1883–1891 Titre : Measuring dielectric constant in highly conductive soils based on surface reflection coefficients Type de document : texte imprimé Auteurs : Renpeng Chen, Auteur ; Wei Xu, Auteur ; Yunmin Chen, Auteur Année de publication : 2010 Article en page(s) : pp. 1883–1891 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Soil  propertiesElectrical  conductivityCoefficientsReflection Résumé : In soils with high electrical conductivities, time domain reflectometry (TDR) principles fail to measure the apparent dielectric constant by travel time analysis. This limits the application of water content measurement of existing TDR technologies on those materials. This paper describes a new approach for determining the dielectric constants in highly conductive soils from surface reflections of TDR signals. The multiple reflections at the interfaces of impedance mismatches in the ASTM standard probe were studied. Extension rods were used to avoid the overlap of the reflections along the probe. A relationship between the reflection coefficient at the soil surface and the apparent dielectric constant of the soil was established theoretically and validated by laboratory experiments. Results indicate that the dielectric constant can be determined with reasonable accuracy from the surface reflection coefficient even for soils with high electrical conductivities, where the conventional travel time analysis fails. Compared with alternative approaches, such as based on inversion model, this new method offers high time efficiency in extending TDR applications in highly conductive soils. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000170 [article] Measuring dielectric constant in highly conductive soils based on surface reflection coefficients [texte imprimé] / Renpeng Chen, Auteur ; Wei Xu, Auteur ; Yunmin Chen, Auteur . - 2010 . - pp. 1883–1891. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 12 (Décembre 2009) . - pp. 1883–1891 Mots-clés : Soil  propertiesElectrical  conductivityCoefficientsReflection Résumé : In soils with high electrical conductivities, time domain reflectometry (TDR) principles fail to measure the apparent dielectric constant by travel time analysis. This limits the application of water content measurement of existing TDR technologies on those materials. This paper describes a new approach for determining the dielectric constants in highly conductive soils from surface reflections of TDR signals. The multiple reflections at the interfaces of impedance mismatches in the ASTM standard probe were studied. Extension rods were used to avoid the overlap of the reflections along the probe. A relationship between the reflection coefficient at the soil surface and the apparent dielectric constant of the soil was established theoretically and validated by laboratory experiments. Results indicate that the dielectric constant can be determined with reasonable accuracy from the surface reflection coefficient even for soils with high electrical conductivities, where the conventional travel time analysis fails. Compared with alternative approaches, such as based on inversion model, this new method offers high time efficiency in extending TDR applications in highly conductive soils. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000170

Secondary compression of municipal solid wastes and a compression model for predicting settlement of municipal solid waste landfills / Yunmin Chen in Journal of geotechnical and geoenvironmental engineering, Vol. 136 N° 5 (Mai 2010) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 5 (Mai 2010) . - pp.706-717 Titre : Secondary compression of municipal solid wastes and a compression model for predicting settlement of municipal solid waste landfills Type de document : texte imprimé Auteurs : Yunmin Chen, Auteur ; Han Ke, Auteur ; Delwyn G. Fredlund, Auteur Année de publication : 2010 Article en page(s) : pp.706-717 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Settlement  Landfill  Biodegradation  Municipal  solid  waste  MSW  Temperature  Landfill  capacity Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : The estimation of the capacity and settlement of landfills is critical to successful site operation and future development of a landfill. This paper reports the results of a study on biodegradation behavior and the compression of municipal solid wastes. An experimental apparatus was developed which had a temperature-control system, a leachate recycling system, a loading system, and a gas and liquid collection system. Experiments were performed both with and without optimal biodegradation for comparative purposes. Test results indicated that settlement resulting from creep was relatively insignificant when the biodegradation process was inhibited. Compression due to decomposition under optimal biodegradation conditions was found to be much larger than compression associated with creep. The biodegradation process was significantly influenced by the operational temperature. A one-dimensional model is proposed for calculating settlement and estimating the capacity of the landfill under relatively optimal biodegradation conditions. The model was developed to accommodate the calculation of settlement in landfills when a multistep filling procedure was used. The calculation method is relatively simple and convenient for design purposes. Simulations of the physical processes showed that enhancing solid waste biodegradation during the filling stage can considerably increase the capacity of the landfill and reduce postclosure settlements. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v136/i5/p706_s1?isAuthorized=no [article] Secondary compression of municipal solid wastes and a compression model for predicting settlement of municipal solid waste landfills [texte imprimé] / Yunmin Chen, Auteur ; Han Ke, Auteur ; Delwyn G. Fredlund, Auteur . - 2010 . - pp.706-717. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 5 (Mai 2010) . - pp.706-717 Mots-clés : Settlement  Landfill  Biodegradation  Municipal  solid  waste  MSW  Temperature  Landfill  capacity Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : The estimation of the capacity and settlement of landfills is critical to successful site operation and future development of a landfill. This paper reports the results of a study on biodegradation behavior and the compression of municipal solid wastes. An experimental apparatus was developed which had a temperature-control system, a leachate recycling system, a loading system, and a gas and liquid collection system. Experiments were performed both with and without optimal biodegradation for comparative purposes. Test results indicated that settlement resulting from creep was relatively insignificant when the biodegradation process was inhibited. Compression due to decomposition under optimal biodegradation conditions was found to be much larger than compression associated with creep. The biodegradation process was significantly influenced by the operational temperature. A one-dimensional model is proposed for calculating settlement and estimating the capacity of the landfill under relatively optimal biodegradation conditions. The model was developed to accommodate the calculation of settlement in landfills when a multistep filling procedure was used. The calculation method is relatively simple and convenient for design purposes. Simulations of the physical processes showed that enhancing solid waste biodegradation during the filling stage can considerably increase the capacity of the landfill and reduce postclosure settlements. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v136/i5/p706_s1?isAuthorized=no