OTHER TYPES OF RETAINING WALLS
There are a variety of retaining walls that are now used in geotechnical and other applications (e.g., landscaping). Some of these are listed below.
Modular Gravity Walls:
- Modular gravity walls consist of a structural container fi lled with materials of various types. These walls are used in projects such as highways, dikes, and channels that conventionally utilize cast-in-place concrete gravity walls. The design method is discussed in Section 15.9. Examples of modular gravity walls are:
- Gabion baskets. Gabion basket walls consist of prefabricated steel wire or polypropylene or polyethylene or nylon baskets fi lled with rocks and stacked horizontal and vertically (Figure). Basket size varies but is normally 2 m in length 3 1 m wide 3 1 m high. Long baskets exceeding 2 m in length are reinforced with diaphragms to strengthen the baskets for ease of construction. Gabion baskets are suitable for gravity walls where rock fi ll material is readily available. Common applications are for erosion protection of banks of rivers and streams, and for retaining walls along roads and highways, especially in rugged terrain. Typically the base width is 0.4 to 0.5 m for backfi lls with f9cs . 308 , 0.5 to 0.7 m for general types of backfi ll, and 0.1 to 1 m for backfi lls with f'cs . 308 . Gabion baskets are usually inclined at about 68 to 108 from the vertical toward the backfi ll.
- Bin walls. Bin walls are gravity walls in which earth fi ll is placed in a bin made from metal (steel) or timber or concrete (Figure 15.33). These walls require a small amount of settlement of the vertical corner members. If the foundation is rigid, a compressible cushion of approximately 200 mm of loose fi ll is placed under the grade plates or concrete base.
- Precast modular concrete walls. These walls are constructed by stacking precast blocks made from concrete and other materials. There is a large variety of blocks, the major differences being the material used to make the blocks, size, and interlocking mechanism.
A crib wall.
In Situ Reinforced Walls:
These walls utilize reinforcing elements to form a composite with the soil. The reinforcing elements are nails or small-diameter cast-in-place concrete piles or small-diameter steel pipe piles. One popular in situ reinforced wall is a soil nail wall. Closely spaced nails are installed by drilling inclined holes into the soil and grouting the holes. Shear stresses from the soil are transferred to the nails and are resisted by tensile forces in the nails. The faces of soil nail walls are shotcrete or precast concrete panels or castin- place concrete.
Chemically Stabilized Earth Walls (CSE):
CSE walls are in situ soils mixed with chemical grouts such as lime or lime-cement mixtures to form columns of overlapping soils. Sometimes reinforcements are added to the soil-grout mixtures before they harden. CSE walls can retain soils up to great depths. They are also used in seepage control.