C.2.2 Deformable facing units
C.2.2.1 Semi elliptical steel units: facing elements of steel sheet (see Figure C.9) formed into elliptical or U-shaped half cylinders. Such units, placed horizontally, are typically 2 to 4 mm thick, 250 mm to 400 mm high and a few metres long. They are fitted with holes along the horizontal edges for connection to the reinforcements.
C.2.2.2 Steel welded wire mesh: Facing units may be formed of open-backed welded wire mesh sections (see Figure C.10), either flat or pre-bent to the required slope angle. These units serve as a formwork during construction. When used for inclined faces, such units may be vegetated to prevent long term erosion of the face. When used for vertical or battered faces, such units may have an inner layer of stone or crushed rock, or be backed with a geosynthetic liner, especially for temporary applications. In some cases such units may be ultimately sprayed with shotcrete, or covered with cast in place concrete. These units may be connected, or not, to the reinforcement. Some types of these facings are proprietary and form part of a system.
C.2.2.3 Gabion baskets: Facing units may also be formed using polymeric geogrid or woven steel wire, galvanised or plastic coated, or galvanised welded wire mesh gabion baskets (See Figure C.11) which are filled with stone or crushed rock. The size of such gabion baskets is usually in the range of 0,5 m to 1,0 m in height, 2 m to 3 m in length and 0,5 m to 1,0 m in depth. The gabion baskets may be supplied with an extended tail that forms a frictional connection to the main reinforcement
C.2.2.4 Tyres: Facing units may also be formed with tyres. These tyres are of similar size and are generally stacked in a staggered arrangement to form the facing.
C.2.3 Soft facings units
C.2.3.1 The most widely used soft facing unit is the so called wrapped facing (See Figure C.12) in which full width reinforcement, such as polymeric grid or geotextile, or woven wire mesh, is extended forward from the reinforced fill to wrap around the face of each intervening layer of fill. Where polymeric grids or woven wire meshes are used these may be faced, or backed, with a suitable geotextile to guard against erosion of the face.
C.2.3.2 To construct such slopes to an acceptable alignment it is common practice to use temporary formwork.
C.2.3.3 Alternatively, the facing units may be formed as fabric containers filled with soil. For these so-called bagged facing units it is preferable to encapsulate the facing unit within the main reinforcement as is the case for the simple wrapped facing.
C.2.3.4 In most cases soft facings units are sprayed or seeded to produce a vegetative cover or, rarely, may be sprayed with shotcrete.