A Numerical Investigation Into The Behaviour Of Reinforced Soil Walls

A review of the available data from the literature relating to the performance of reinforced soil walls indicates that there are some significant deviations between field observations and the assumptions considered in current analytical and design methods. Furthermore, there are inconsistencies evident in the interpretation of the data obtained from instrumented cases relating to the stresses in the reinforced soil, the force in the reinforcement and the state of stress within the reinforced soil mass.;A comparison of the results from twelve current analytical and design methods with the performance of four reinforced soil walls case histories suggests that these methods are inadequate to accurately model reinforced soil walls under working stress conditions. A few methods do provide good prediction for the forces in the reinforcement for simple walls (e.g. walls with limited influence from the facing and the foundation) in terms of the total force required for horizontal force equilibrium when the wall is approaching failure. However, none of the methods give a good prediction of the force distribution between the layers of the reinforcement.;Examining the results from a hypothetical full facing panel soil wall constructed on a rigid foundation reveals that there are two equilibrium conditions to be considered in reinforced soil walls, these are similar to those considered for conventional rigid retaining walls. One is related to the internal equilibrium of the reinforced soil mass, the other is related to external equilibrium of the facing. For a typical wall with a reinforcement length to wall height of 0.7, the total force required for equilibrium is largely independent of material properties other than the friction angle of the backfill soil and can be determined using calculations based on Rankine active earth pressure theory. Likewise external equilibrium of the facing is also largely independent of material properties and can be determined from a Coulomb active wedge analysis. However, the forces for both equilibrium conditions increase significantly when the reinforcement length to wall height ratio is small.;Material properties and wall geometry have a significant effect on the distribution of force in the reinforcement layers. The variation in force distribution stems from the requirements to satisfy static equilibrium conditions in response to changes in the stresses in the reinforced soil due to a change in material property and wall geometry. Without considering these interactions, it is difficult to determine the force in the reinforcement precisely.;The numerical results indicate that the deformation in the reinforced soil wall can be significantly affected by the presence of the unreinforced soil above the zero force line which exerts pressure on the reinforced soil mass and causes shear deformation in the reinforced soil. This shear deformation must be considered for accurate assessment of the deformation at the wall face.;There is indication from the numerical results that the most commonly used reinforcement length to wall height ratio of 0.7 should be used with a minimum soil friction angle of 35{dollar}\sp\circ{dollar}