C.3.4 Review of main systems (p. III)
Table C.8 - STEEL WIRE GRID
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REINFORCEMENT | MAIN APPLICATIONS | |
| Mostly used with polymeric geogrids, steel strip, ladder or grid fill reinforcement. | Vertical, battered or inclined, possibly tiered, earth retaining structures. Inclined faces are usually seeded to give vegetation cover. Vertical or battered faces are usually backed with geotextile (particularly for temporary applications) or with a layer of stone or crushed rock. |
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| TECHNOLOGY | LONGITUDINAL FLEXIBILITY | TRANSVERSAL FLEXIBILITY | FILL MATERIAL |
| Open backed steel grid or steel mesh sections, either flat or pre- bent to required slope angle. | Generally high resistance to longitudinal differential settlement. | Semi-flexible system: low bending stiffness and vertical compressibility allow the facing to deform vertically and to accompany moderate settlement of the retained fill. | Most commonly used with granular fill material. Intermediate fills can also be used for some applications (see Annex A for guidance). |
| TOLERANCES | OTHER COMMENTS | ||
| Alignment ± 100 mm |
Differential settlement ~ 2 % |
Compressibility ~ 5 % |
A filter may be required between fill and crushed rock, if used at the face. |
Table C.9 - GABION BASKETS
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REINFORCEMENT | MAIN APPLICATIONS | |
| Mostly used with layers of metallic meshes, polymeric geogrids and geotextiles (woven, or special nonwoven or compound fabrics). The reinforcement is connected to or continuous with the base of the gabion basket. |
Mostly used for vertical or battered, possibly tiered walls. | ||
| TECHNOLOGY | LONGITUDINAL FLEXIBILITY | TRANSVERSAL FLEXIBILITY | FILL MATERIAL |
| Gabion baskets may be formed from steel welded or woven wire mesh, or polymeric geogrids. The gabion baskets are filled with stone or crushed rock. |
Generally high resistance to longitudinal differential settlement. | The compressibility of the gabion baskets is controlled by the nature and placement of the material used to fill the baskets. This generally makes the system semi flexible. | Most commonly used with granular fill material. Intermediate fills can also be used for some applications (see Annex A for guidance). |
| TOLERANCES | OTHER COMMENTS | ||
| Alignment ± 100 mm |
Differential settlement ~ 2 % |
Compressibility ~ 5 % |
A filter is usually required between the fill and the gabion baskets. |
Table C.10 - WRAPPED AROUND (without formwork)
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REINFORCEMENT | MAIN APPLICATIONS | |
| Geogrids, geotextiles, woven wire mesh. | Shallow slopes, around 1/1. In most cases such slopes are sprayed or seeded to produce a vegetative cover. |
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| TECHNOLOGY | LONGITUDINAL FLEXIBILITY | TRANSVERSAL FLEXIBILITY | FILL MATERIAL |
| Facing made of polymeric grids or geotextiles, or woven wire mesh. Built in horizontal courses. Where polymeric grids or woven wire mesh are used, these may be backed with a suitable geotextile to guard against erosion. |
High tolerance to longitudinal differential settlement. | Flexible system | May include fine materials when draining geotextiles are used. |
| TOLERANCES | OTHER COMMENTS | ||
| Alignment ± 200 mm Construction tolerances decrease with increasing height and decreasing fill quality. |
Differential settlement ~ 5 %. |
Compressibility ≥ 10 %. |
Risk from vandalism and fire, reduced by vegetative or shotcrete cover. |
Table C.11 - WRAPPED AROUND (with formwork) or BAGGED
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REINFORCEMENT | MAIN APPLICATIONS | |
| Geogrids, geotextiles, woven wire mesh. | Inclined or battered walls. Such slopes are often sprayed or seeded to produce a vegetative cover, or faced with shotcrete. Also used for vertical walls, with an independent concrete cladding in front. |
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| TECHNOLOGY | LONGITUDINAL FLEXIBILITY | TRANSVERSAL FLEXIBILITY | FILL MATERIAL |
| Facing made of polymeric grids or geotextiles, or woven wire mesh. Built in horizontal courses. To construct such slopes to an acceptable alignment it is common practice to use temporary formwork. |
High tolerance to longitudinal differential settlement (except once possibly covered with shotcrete). | Flexible system. | May include fine materials when draining geotextiles are used. |
| TOLERANCES | OTHER COMMENTS | ||
| Alignment ± 100 mm Fair construction tolerances obtained with care and better quality fill. |
Differential settlement ~ 5 % |
Compressibility ≥ 10 % |
Risk from vandalism and fire reduced by vegetative or shotcrete cover. |
Table C.12 - IN-SITU CONCRETE FACING
 |
REINFORCEMENT | MAIN APPLICATIONS | |
| See comments for steel wire grid facing and wrapped around facing. | Inclined or battered walls. | ||
| TECHNOLOGY | LONGITUDINAL FLEXIBILITY | TRANSVERSAL FLEXIBILITY | FILL MATERIAL |
| Used occasionally as adjunct to steel wire grid facing or wrapped around facing. | Near zero tolerance to longitudinal differential settlement once the concrete face is cast. | Near zero tolerance to differential settlement between facing and reinforcement once the concrete face is cast. | See comments for steel wire grid facing and wrapped around facing. |
| TOLERANCES | OTHER COMMENTS | ||
| Alignment ± 50 mm |
Differential settlement ~ 0 % |
Compressibility ~ 0 % |
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