**1. Introduction**

Reinforced soil walls (RSW) are retaining structures composed by facing, compacted backfill and usually geosynthetic reinforcements. Compacted soils have good strength in terms of compression solicitation, but they have a very low tensile strength. Thus, similar to the reinforced concrete, the use of fabrics as reinforcement is intended to provide enough tension resistance to the composite material. RSW structures can be built with a wide variety of fabrics (geosynthetics). Those fabrics are specially developed and have different applications in geotechnical engineering. **Figure 1** shows some examples of geosynthetics used in RSW construction as reinforcement.

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

overturning, bearing capacity and general failure and (b) internal stability. The internal stability consists in the comparison of the mobilized load in the reinforcements (geosynthetic) with the tension strength of those ones. There are some methods to evaluate the mobilized load in the reinforcements, such as [1–5]. Through case studies, field instrumentation, physical and numerical modeling [6–11] have been demonstrated that among these methods the more suitable are the ones proposed in [4, 5]. These methods explicitly consider soil and reinforcement properties, the effect of compaction operation, and the relative stiffness between soil and reinforcement. The method described in [5] is based on the one developed by Ehrlich and Mitchell [4]; this method uses simple equations and may take in the calculation facing inclination into consideration.

Behavior of Reinforced Soil Wall Built with Fabrics http://dx.doi.org/10.5772/intechopen.79239 95

**Figure 3** shows different concepts of facing elements. In the RSW structures, facing has a secondary function, and it is used to avoid erosion and localized soil failure near to the face, besides providing suitable visual appearance. Precast concrete block-face is usually used in RSWs with geogrid reinforcements (**Figure 3c**). Precast concrete block-face is also used in the case of RSW with geosynthetic wrap-around facing (**Figure 3a**). This block-facing is applied after the end of the wall construction, and it is needed to protect geosynthetics from degradation due to exposure to ultraviolet rays and vandalism. Depending on its rigidity, the face may be capable to absorb part of the tension that would be supported by the reinforcements. Nevertheless, the design of internal stability is usually done without consideration of the facing contribution to the global stability, if it exists. Note that this approach is by the side of safety [6]. Moreover, enough drainage must be employed in order to guarantee no positive

**Figure 3.** Typical facing elements: (a) geosynthetic wrap-around facing before protection application (courtesy: Ober geosynthetics); (b) precast-concrete panels (courtesy: Reinforced Earth Company); (c) precast-concrete blocks facing; and

(d) steel mesh facing filled with stones (courtesy: Paulo Brugger).

**Figure 1.** Examples of geosynthetics used for RSW construction as reinforcement: (a) geogrid; (b) nonwoven geotextile; (c) woven geotextile.

The backfill used for reinforced soil wall construction could be purely sands or even soils that contain high percentage of fines. In Brazil, due to the abundance of residual fine-grained soils, it is a common practice to build RSW using this kind of soil. This kind of soils, in spite of its high percentage of fines, has high strength resistance, presents good workability, and achieves a proper density during compaction. **Figure 2** shows the basic concept of RSW; the geosynthetics link the active zone (the unstable zone) to the resistant zone. Design should provide enough reinforcements in order to guarantee no failure or pullout of reinforcements from the resistant zone. Both zones liked together works like a block that may be considered as a conventional retaining wall that provides the stabilization of the nearby nonreinforced soil mass. The mobilized load along the reinforcements is variable, and the location of the points of maximum tension defines the potential failure surface that separates the active and passive zones. **Figure 2** also indicates the shape of the potential failure surface that varies with the stiffness of reinforcements.

The design of an RSW comprises basically two verifications: (a) external stability that is basically the same concept used for the conventional retaining walls, i.e., stability analyses for sliding and

**Figure 2.** Basic concept of RSW and the potential failure surface: for extensible (a) and rigid (b) reinforcements.

overturning, bearing capacity and general failure and (b) internal stability. The internal stability consists in the comparison of the mobilized load in the reinforcements (geosynthetic) with the tension strength of those ones. There are some methods to evaluate the mobilized load in the reinforcements, such as [1–5]. Through case studies, field instrumentation, physical and numerical modeling [6–11] have been demonstrated that among these methods the more suitable are the ones proposed in [4, 5]. These methods explicitly consider soil and reinforcement properties, the effect of compaction operation, and the relative stiffness between soil and reinforcement. The method described in [5] is based on the one developed by Ehrlich and Mitchell [4]; this method uses simple equations and may take in the calculation facing inclination into consideration.

**Figure 3** shows different concepts of facing elements. In the RSW structures, facing has a secondary function, and it is used to avoid erosion and localized soil failure near to the face, besides providing suitable visual appearance. Precast concrete block-face is usually used in RSWs with geogrid reinforcements (**Figure 3c**). Precast concrete block-face is also used in the case of RSW with geosynthetic wrap-around facing (**Figure 3a**). This block-facing is applied after the end of the wall construction, and it is needed to protect geosynthetics from degradation due to exposure to ultraviolet rays and vandalism. Depending on its rigidity, the face may be capable to absorb part of the tension that would be supported by the reinforcements. Nevertheless, the design of internal stability is usually done without consideration of the facing contribution to the global stability, if it exists. Note that this approach is by the side of safety [6]. Moreover, enough drainage must be employed in order to guarantee no positive

**Figure 3.** Typical facing elements: (a) geosynthetic wrap-around facing before protection application (courtesy: Ober geosynthetics); (b) precast-concrete panels (courtesy: Reinforced Earth Company); (c) precast-concrete blocks facing; and (d) steel mesh facing filled with stones (courtesy: Paulo Brugger).

**Figure 2.** Basic concept of RSW and the potential failure surface: for extensible (a) and rigid (b) reinforcements.

The backfill used for reinforced soil wall construction could be purely sands or even soils that contain high percentage of fines. In Brazil, due to the abundance of residual fine-grained soils, it is a common practice to build RSW using this kind of soil. This kind of soils, in spite of its high percentage of fines, has high strength resistance, presents good workability, and achieves a proper density during compaction. **Figure 2** shows the basic concept of RSW; the geosynthetics link the active zone (the unstable zone) to the resistant zone. Design should provide enough reinforcements in order to guarantee no failure or pullout of reinforcements from the resistant zone. Both zones liked together works like a block that may be considered as a conventional retaining wall that provides the stabilization of the nearby nonreinforced soil mass. The mobilized load along the reinforcements is variable, and the location of the points of maximum tension defines the potential failure surface that separates the active and passive zones. **Figure 2** also indicates the

**Figure 1.** Examples of geosynthetics used for RSW construction as reinforcement: (a) geogrid; (b) nonwoven geotextile;

(c) woven geotextile.

94 Engineered Fabrics

shape of the potential failure surface that varies with the stiffness of reinforcements.

The design of an RSW comprises basically two verifications: (a) external stability that is basically the same concept used for the conventional retaining walls, i.e., stability analyses for sliding and pore-pressures inside the reinforced soil mass. The drainage system is often composed by a vertical layer of gravel behind the face and a horizontal layer at the RSW bottom.
