There have been ongoing arguments whether heavy blocks and/or facing connection enhancement elements, such as pins, lips, or keys, are needed for facing stability of segmental reinforced soil walls with geosynthetic reinforcement. This study was undertaken to examine facing connection forces for vertical or near vertical segmental reinforced soil walls with purely friction connections. In the study, the lateral earth pressure was assumed to be the Rankine active earth pressure-an assumption that has been employed by most current design methods of reinforced soil walls with extensible reinforcement. Based on force equilibrium, the driving forces and resisting forces at facing connections are derived for situations where reinforcement is at every course of facing blocks and at every three courses of facing blocks. For the latter, both the connection forces at geosynthetic-block interface and at block-block interface are considered. Based on these connection force equations, generalized equations of driving and resisting forces for any number courses of blocks between adjacent reinforcement layers are developed. Using the generalized connection force equations, comparisons of driving and resisting forces for some common parameter values and under typical conditions of reinforced soil walls were performed. The significance of reinforcement spacing, as well as the need, or lack thereof, for heavy facing blocks and/or additional connection measures on facing stability is discussed. The benefit of small reinforcement spacing is demonstrated. A common perception that a higher wall is more susceptible to connection failure is true only for segmental walls with larger reinforcement spacing.

The dynamic response of a mechanically stabilized earth wall to the passing of a high-speed train is modelled using the finite element method. A three-dimensional analysis is carried out, using a specific framework that allows performing the analysis with a moderate computational effort. In the first place, a so-called multiphase approach is used to take into account the reinforcing strips. The moving load is taken into account by performing the calculation in a mobile referential using the properties of symmetry of the train cars and a simplifying assumption of periodicity for the whole train. We also assume a steady state. A partial validation of the approach is obtained by means of a comparison with an analytical solution. The quick increase in displacements induced by the train passing when the speed comes close to the celerity of Rayleigh waves clearly appears in the results. The vertical displacements, vertical stresses in the backfill,tensile forces in the strips and the influence of the stiffness of the soil are discussed.La réponse dynamique d'un mur en sol renforcé au passage d'un train à grande vitesse est modélisée par éléments finis. Une analyse tridimensionnelle est effectuée, dans un cadre spécifique qui permet de faire le calcul pour un cout de calcul acceptable : d'une part, on utilise le modèle multiphasique pour prendre en compte les armatures ; d'autre part, on prend en compte le déplacement de la charge en effectuant le calcul dans un référentiel mobile ; enfin on tire parti des propriétés de symétrie des voitures et on fait une hypothèse simplificatrice de périodicité du train. On fait de plus l'hypothèse que l'on a atteint un régime permanent. Une validation partielle est obtenue par comparaison avec une solution analytique. L'augmentation des déplacements induits par le passage du train lorsque sa vitesse s'approche de la célérité des ondes de Rayleigh apparait clairement dans les résultats. Les déplacements verticaux, les contraintes verticales dans le remblai, les efforts de traction dans les armatures et l'influence de la raideur du remblai sont discutées