There are instances when one MSE wall is built on top of another. In certain instances, these walls can be considered to be two independent structures, each requiring its own internal design and external stability. The global stability of the slope must be sufficiently stable so as not to undermine the stability of the entire embankment.
Figure 8.36 shows a superimposed structure. The walls are such that the load of the upper wall level serves as a surcharge load on the lower wall. Each wall is independently designed.
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FIGURE 8.35 Foundation pressure for MSE wall calculated by the AASHTO method based on Meyerhof. (From the Reinforced Earth Co., with permission) |
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FIGURE 8.36 Superimposed MSE walls. (From the Reinforced Earth Co., with permission) |
This design approach does not hold when the MSE structures are directly superimposed, one on another, as shown in Fig. 8.37. Such terraced arrangements are sometimes used for high walls. These offset structures are obviously similar to a single embankment with a sloping face. They exhibit essentially the same overall behavior, and are designed as sloping faced walls.
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FIGURE 8.37 Terraced MSE wall. (From the Reinforced Earth Co., with permission) |
