Keywords: brick faced retaining wall, soil reinforcement, face deformation, design method, failure mechanism, geosynthetics.

Soil reinforcement with the inclusions of tensile strength elements is a very old technique. Important progresses were made in recent years, regarding the understanding of the behaviour and especially the development of different construction techniques and materials. The study described herein is concerned with brick faced retaining walls with a set of short geotextile sheets extended from the rear face of the wall into the backfill at appropriate vertical spacing. These walls combine the advantages of a robust and durable brick masonry wall with the soil reinforcement technique. This composite structure shows a significantly higher strength when compared to more traditional structures. Furthermore it shows a slow and progressive failure mechanism in opposition to the sudden and catastrophic failure of unreinforced walls.

The soil reinforcement interaction develops as the retaining walls are deforming. This deformation needs to be kept below acceptable values. The introduction of the serviceability concept is particularly important for brick faced retaining walls reinforced with geotextiles because these reinforcing elements are very extensible when compared with other reinforcement materials, like metallic. The analysis of the deformations can be done by numerical methods, but these are costly because of the large time consumed for preparing and processing calculations, high demand of a sophisticated characterization of materials, interfaces, etc. The work carried out and described herein consists on the development of a very simple method to predict the face deformations of the brick faced retaining wall reinforced with geotextiles. The model developed for predicting deformations of the brick faced retaining walls reinforced with geotextiles is based on a theoretical model that considers a beam simply leaning on flexible supports (connecting rods) that simulates the reinforcement. The beam can rotate at the base, as the wall also does.

The beam deformability depends on the wall face bending stiffness and the reinforcement tensile strength and stiffness define the axial stiffness of the flexible supports. The beam is under a load diagram defined by the earth horizontal pressure acting on the rear face of the wall. The load diagram acting on the beam simulates closely the observed diagram of earth pressure as this diagram depends already on the deformability of the reinforcement, of the backfill and of the face of the wall, but, most important, the compatibility between all these deformations. The earth pressure corresponds to the at rest state near the top of the wall and tends to the active state near the base. Furthermore, local variations were identified, as different values of the earth pressure were measured immediately on top and bellow the reinforcing elements.

A good agreement was achieved between the proposed method and the laboratory results for all of the geometries of the reinforcement. Comparisons between these results and those obtained from the numerical analysis leads to the conclusion that the simple method simulates better the deformations than the numerical analysis. Nevertheless the simplicity of the model is shown to be very versatile and the results compare well with previous laboratory measurements.

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