Mechanically Stabilized Earth (MSE) walls are earth retaining structures that are constructed by placing alternating layers of reinforcement and compacted soil behind a facing element to form a composite material which acts integrally to restrain lateral forces. MSE walls are gravity structures that are relatively flexible and can tolerate horizontal and vertical deformations. Although MSE walls can be used in cut situations they are most efficient in fill or embankment applications. Figure 1 is an example of an MSE wall using pre-cast concrete facing elements.
FIGURE 1 Pre-Cast Concrete Panel MSE Wall.
Figure 2 illustrates the three primary MSE wall components. These three components work together to form the composite structure referred to as MSE. Because MSE is an integration of components, MSE walls are designed for external, internal, and compound stability. External stability analysis addresses sliding, bearing capacity, eccentricity, and overall stability modes of failure. Internal stability analysis addresses reinforcement rupture and interaction with reinforced fill and connection strength. Stability analyses also identify possible compound failure modes which initiate outside the reinforced zone and exit through the reinforcement and facing.
Reinforced fill is the soil that is used to construct the wall. Although it can be composed of a wide range of soil types, a well graded granular soil is the preferred material due to its strength, drainage, and durability properties. A well graded granular soil is also preferable for constructability and interaction with the reinforcement elements. Soils that are poorly graded or have a significant percent of fines (smaller than the No. 200 sieve) are much more moisture sensitive and are very difficult to place and compact.
Reinforcement elements are inclusions which are placed in layers within the fill material. Through their interaction with the surrounding soil and their tensile capacity they confine the soil and provide reinforcement. Reinforcing elements are made out of steel or geosynthetic materials. They are fabricated as strips, bar mats, geogrids, or fabrics and have a wide range of tensile strength and stiffness.
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