Facing units and systems
C.1.1 Reinforced fill is constructed using successive layers of compacted, selected fill incorporating intervening layers of horizontal or sub-horizontal fill reinforcement placed at spacing required by the design.
C.1.2 Reinforced fill earth retaining structures, with a vertical, battered or inclined face (see Figure C.1), require a facing to retain the fill between the reinforcing layers. Depending on the particular system, certain layers of fill reinforcements may however not be connected to the facing.
C.1.3 On shallow reinforced slopes, facing is generally not necessary. Such slopes are usually protected by vegetation with / without erosion control materials.
C.1.4 The facing can be constituted of either hard units (typically made of concrete), or deformable units (typically made from metal, steel grid or mesh, or gabion baskets), or soft units (typically made from geosynthetic sheets or grids, or woven wire mesh).
C.1.5 Where hard or deformable facing units are used, these serve as a formwork against which the selected fill is placed and compacted. Where soft facing units are used, it is generally necessary to employ temporary formwork to maintain the face alignment during the construction of walls or steep slopes.
|1 Earth retaining structures||8 Some specific types of facings: panels, blocks, 1/2 elliptical steel units, gabions|
|2 Reinforced slopes||9 Specific types of sloping panel, eg for bulk storage|
|3 Vertical||10 Some common types of facings: planter units, wire mesh, wrapped around|
|4 Vertical wall||11 No facing, erosion protection may be required|
|5 Battered wall||12 Line of 4:1 face slope angle|
|6 Inclined wall Steep slope||13 Line of 1:1 face slope angle|
|7 Shallow slope|
C.2 Facing units
C.2.1 Hard facing units
C.2.1.1 Hard facing units are usually produced in precast concrete, either un-reinforced or reinforced (See Figure C.1).
C.2.1.2 Concrete facing units may be full height panels, partial height panels, sloping panels, planter units, or segmental blocks. Many types of concrete facing units are proprietary and form part of proprietary systems.
C.2.1.3 The reinforcements are connected to the units either by means of devices embedded or inserted into the concrete units, or they are simply clamped between the units.
C.2.1.4 Full height panels: As the name suggests, full height panels (see Figure C.2 a) are precast to the required full height of the specific reinforced fill wall to be constructed. The breadth of full height panels is typically in the range 1 to 3 m and the thickness in the range 100 to 200 mm.
C.2.1.5 Partial height panels: Partial height panels (See Figure C.3) are the most common and typically have heights in the range 1 to 2 m and thickness in the range 100 to 200 mm. Distinctive shapes correspond to specific ways of fitting panels together, and to particular construction procedures. Simple rectangular shapes are also available. The panels are fitted with connecting devices embedded into the back face. The edges are usually provided with nibs and recesses, or tongues and grooves.
C.2.1.6 Vertical panels with preferred rupture lines can also be used (see Figure C.4).
C.2.1.7 Sloping panels: Sloping precast concrete units (See Figure C.5), equipped with inner buttresses sitting on the compacted fill. The length is usually of the order of 3 m and the height, measured along the slope, of the order of 1,5 m. The inclination is commonly between 50° and 65° to the horizontal. The units are equipped with connecting devices embedded into the buttresses.
1 Front face
C.2.1.8 Planter units: Precast concrete generally made of a sloping slab (See Figure C.6) supported by outer buttresses or side flanges sitting (partially or totally) on the compacted fill. The length is usually of the order of 2 m and the nominal height between 0,5 and 1 m. The units come with connecting devices embedded at the back.
1 Front face
C.2.1.9 Segmental blocks: Facing units in the form of precast or dry cast un-reinforced concrete blocks (see Figure C.7) are usually referred to as modular blocks or segmental blocks. Units may be manufactured solid, or with cores. The mass of these units commonly ranges from 20 and 50 kilos. Unit heights typically range from 150 mm to 250 mm, exposed face length usually varies from 200 mm to 500 mm. Depending on the type of reinforcement, blocks may be provided with connecting accessories (pins, rake). Otherwise the reinforcement is clamped between successive courses of blocks.
C.2.1.10 King post and concrete planking: Horizontal concrete planking slid between universal column posts (see Figure C.8). The reinforcement is usually connected to a bar that slides on the rear flanges of the king posts or clamped between the concrete planks with a lock on the outside face.