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Required unfactored strength of geosynthetic in reinforced earth structures / Leshchinsky, Dov in Journal of geotechnical and geoenvironmental engineering, Vol. 136 N° 2 (Fevrier 2010) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 2 (Fevrier 2010) . - pp. 281-289 Titre : Required unfactored strength of geosynthetic in reinforced earth structures Type de document : texte imprimé Auteurs : Leshchinsky, Dov, Auteur ; Fan Zhu, Auteur ; Christopher L. Meehan, Auteur Article en page(s) : pp. 281-289 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Reinforced  soil  Slope  stability  Geosynthetics  Limit  equilibrium Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Current reinforced earth structure designs arbitrarily distinguish between reinforced walls and slopes, that is, the batter of walls is 20° or less while in slopes it is larger than 20°. This has led to disjointed design methodologies where walls employ a lateral earth pressure approach and slopes utilize limit equilibrium analyses. The earth pressure approach used is either simplified (e.g., ignoring facing effects), approximated (e.g., considering facing effects only partially), or purely empirical. It results in selection of a geosynthetic with a long-term strength that is potentially overly conservative or, by virtue of ignoring statics, potentially unconservative. The limit equilibrium approach used in slopes deals explicitly with global equilibrium only; it is ambiguous about the load in individual layers. Presented is a simple limit equilibrium methodology to determine the unfactored global geosynthetic strength required to ensure sufficient internal stability in reinforced earth structures. This approach allows for seamless integration of the design methodologies for reinforced earth walls and slopes. The methodology that is developed accounts for the sliding resistance of the facing. The results are displayed in the form of dimensionless stability charts. Given the slope angle, the design frictional strength of the soil, and the toe resistance, the required global unfactored strength of the reinforcement can be determined using these charts. The global strength is then distributed among individual layers using three different assumed distribution functions. It is observed that, generally, the assumed distribution functions have secondary effects on the trace of the critical slip surface. The impact of the distribution function on the required global strength of reinforcement is minor and exists only when there is no toe resistance, when the slope tends to be vertical, or when the soil has low strength. Conversely, the impact of the distribution function on the maximum unfactored load in individual layers, a value which is typically used to select the geosynthetics, can result in doubling its required long-term strength. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JGGEFK&smode=strres [...] [article] Required unfactored strength of geosynthetic in reinforced earth structures [texte imprimé] / Leshchinsky, Dov, Auteur ; Fan Zhu, Auteur ; Christopher L. Meehan, Auteur . - pp. 281-289. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 2 (Fevrier 2010) . - pp. 281-289 Mots-clés : Reinforced  soil  Slope  stability  Geosynthetics  Limit  equilibrium Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Current reinforced earth structure designs arbitrarily distinguish between reinforced walls and slopes, that is, the batter of walls is 20° or less while in slopes it is larger than 20°. This has led to disjointed design methodologies where walls employ a lateral earth pressure approach and slopes utilize limit equilibrium analyses. The earth pressure approach used is either simplified (e.g., ignoring facing effects), approximated (e.g., considering facing effects only partially), or purely empirical. It results in selection of a geosynthetic with a long-term strength that is potentially overly conservative or, by virtue of ignoring statics, potentially unconservative. The limit equilibrium approach used in slopes deals explicitly with global equilibrium only; it is ambiguous about the load in individual layers. Presented is a simple limit equilibrium methodology to determine the unfactored global geosynthetic strength required to ensure sufficient internal stability in reinforced earth structures. This approach allows for seamless integration of the design methodologies for reinforced earth walls and slopes. The methodology that is developed accounts for the sliding resistance of the facing. The results are displayed in the form of dimensionless stability charts. Given the slope angle, the design frictional strength of the soil, and the toe resistance, the required global unfactored strength of the reinforcement can be determined using these charts. The global strength is then distributed among individual layers using three different assumed distribution functions. It is observed that, generally, the assumed distribution functions have secondary effects on the trace of the critical slip surface. The impact of the distribution function on the required global strength of reinforcement is minor and exists only when there is no toe resistance, when the slope tends to be vertical, or when the soil has low strength. Conversely, the impact of the distribution function on the maximum unfactored load in individual layers, a value which is typically used to select the geosynthetics, can result in doubling its required long-term strength. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JGGEFK&smode=strres [...]

Resultant force of lateral earth pressure in unstable slopes / Leshchinsky, Dov in Journal of geotechnical and geoenvironmental engineering, Vol. 136 N° 12 (Décembre 2010) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 12 (Décembre 2010) . - pp. 1655-1663 Titre : Resultant force of lateral earth pressure in unstable slopes Type de document : texte imprimé Auteurs : Leshchinsky, Dov, Auteur ; Fan Zhu, Auteur Année de publication : 2011 Article en page(s) : pp. 1655-1663 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Coulomb  Caquot  and  Kerisel  Lateral  earth  pressure  Limit  equilibrium  Slope  instability Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Traditionally, resultant force of lateral earth pressure serves as the basis for design of nearly vertical walls. Conversely, slopes are designed to be internally stable using a factor of safety approach. However, with the availability of heavy facing elements such as gabions, steep slopes are increasingly being constructed. Steep slopes are considered to be unstable unless supported; that is, such slopes require facings to resist lateral earth pressure. Extending Coulomb’s formulation to such slopes may not be conservative as a planar slip surface may not be critical. Presented are the results of a formulation to find the resultant lateral force which utilizes a log spiral failure mechanism. Unlike Caquot and Kerisel or Coulomb, the soil-facing interface friction is assumed to act on segments of vertical surface only, thus replicating the geometry of stacked rectangular facing units. Given the batter, the backslope, the height, the interface friction, and the unit weight and design friction angle of the backfill, one can quickly determine the corresponding lateral earth pressure coefficient. Formulation assuming the interface friction is acting on an imaginary surface inclined at the batter angle, essentially equivalent to Coulomb and Caquot and Kerisel, is also presented. Its results show that for batters up to 20°, the common approach of using the Coulomb method, including the assumed interface friction direction to coincide with the batter, yields results that are quite close to those stemming from the log spiral analysis. Hence, use of Coulomb’s analysis for such small batters is reasonable as its formulation is simple. However, the lateral resultant is grossly underestimated for larger batters, especially when Coulomb analysis is used. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v136/i12/p1655_s1?isAuthorized=no [article] Resultant force of lateral earth pressure in unstable slopes [texte imprimé] / Leshchinsky, Dov, Auteur ; Fan Zhu, Auteur . - 2011 . - pp. 1655-1663. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 12 (Décembre 2010) . - pp. 1655-1663 Mots-clés : Coulomb  Caquot  and  Kerisel  Lateral  earth  pressure  Limit  equilibrium  Slope  instability Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Traditionally, resultant force of lateral earth pressure serves as the basis for design of nearly vertical walls. Conversely, slopes are designed to be internally stable using a factor of safety approach. However, with the availability of heavy facing elements such as gabions, steep slopes are increasingly being constructed. Steep slopes are considered to be unstable unless supported; that is, such slopes require facings to resist lateral earth pressure. Extending Coulomb’s formulation to such slopes may not be conservative as a planar slip surface may not be critical. Presented are the results of a formulation to find the resultant lateral force which utilizes a log spiral failure mechanism. Unlike Caquot and Kerisel or Coulomb, the soil-facing interface friction is assumed to act on segments of vertical surface only, thus replicating the geometry of stacked rectangular facing units. Given the batter, the backslope, the height, the interface friction, and the unit weight and design friction angle of the backfill, one can quickly determine the corresponding lateral earth pressure coefficient. Formulation assuming the interface friction is acting on an imaginary surface inclined at the batter angle, essentially equivalent to Coulomb and Caquot and Kerisel, is also presented. Its results show that for batters up to 20°, the common approach of using the Coulomb method, including the assumed interface friction direction to coincide with the batter, yields results that are quite close to those stemming from the log spiral analysis. Hence, use of Coulomb’s analysis for such small batters is reasonable as its formulation is simple. However, the lateral resultant is grossly underestimated for larger batters, especially when Coulomb analysis is used. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v136/i12/p1655_s1?isAuthorized=no