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Design of micropiles for tunnel face reinforcement / Núria M. Pinyol in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 1 (Janvier 2012) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 1 (Janvier 2012) . - pp. 89-99 Titre : Design of micropiles for tunnel face reinforcement : Undrained upper bound solution Type de document : texte imprimé Auteurs : Núria M. Pinyol, Auteur ; Eduardo E. Alonso, Auteur Année de publication : 2012 Article en page(s) : pp. 89-99 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Tunnel  Micropile  Plasticity  Upper  bound  Design  Case  history Résumé : The stability of tunnel faces supported by an umbrella of subhorizontal micropiles is analyzed by means of the upper bound theorem of plasticity. The micropiles are considered beams subjected to the kinematic motion imposed by the assumed failure mechanism. The limiting resistance of the supporting beams is first addressed. The failure mechanism imposes a displacement pattern on the beam, which is similar to the response of vertical piles subjected to horizontal load. The mechanism of beam deformation was included into the overall instability mechanism for the tunnel face stability. Limiting conditions of the beam under undrained conditions are used. A general minimization process associated with the upper bound formulation is developed. Stability conditions are described in dimensionless parameters and plotted in ready-to-use design charts. In particular, a dimensionless micropile coefficient, which includes all the relevant design parameters of the umbrella, could be isolated and plotted in undrained soil strength and tunnel geometry. A real face failure is finally described, and the required supporting umbrella is designed on the basis of the developed procedure. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v138/i1/p89_s1?isAuthorized=no [article] Design of micropiles for tunnel face reinforcement : Undrained upper bound solution [texte imprimé] / Núria M. Pinyol, Auteur ; Eduardo E. Alonso, Auteur . - 2012 . - pp. 89-99. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 1 (Janvier 2012) . - pp. 89-99 Mots-clés : Tunnel  Micropile  Plasticity  Upper  bound  Design  Case  history Résumé : The stability of tunnel faces supported by an umbrella of subhorizontal micropiles is analyzed by means of the upper bound theorem of plasticity. The micropiles are considered beams subjected to the kinematic motion imposed by the assumed failure mechanism. The limiting resistance of the supporting beams is first addressed. The failure mechanism imposes a displacement pattern on the beam, which is similar to the response of vertical piles subjected to horizontal load. The mechanism of beam deformation was included into the overall instability mechanism for the tunnel face stability. Limiting conditions of the beam under undrained conditions are used. A general minimization process associated with the upper bound formulation is developed. Stability conditions are described in dimensionless parameters and plotted in ready-to-use design charts. In particular, a dimensionless micropile coefficient, which includes all the relevant design parameters of the umbrella, could be isolated and plotted in undrained soil strength and tunnel geometry. A real face failure is finally described, and the required supporting umbrella is designed on the basis of the developed procedure. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v138/i1/p89_s1?isAuthorized=no