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Reinforced Earth or Mechanically stabilized earth (MSE) is soil constructed with artificial reinforcing. It can be used for retaining walls, bridge abutments, dams, seawalls, and dikes. Although the basic principles of MSE has been used throughout history, MSE was developed in its current form in the 1960s. The reinforcing elements used can vary but include steel and geosynthetics. The reinforcement materials of MSE can vary. Originally, long steel strips 50 to 120 mm (2 to 5 in) wide were used as reinforcement. These strips are sometimes ribbed, although not always, to provide added resistance. Sometimes steel grids or meshes are also used as reinforcement. Several types of geosynthetics can be used including geogrids and geotextiles. The reinforcing geosynthetics can be made out of high density polyethylene, polyester, and polypropylene. These materials may also be ribbed and come in varying sizes and strengths.
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Design of Reinforced Earth Structures
Reinforced Soil Structure consists of facing panels and compacted fill incorporating reinforcing elements (e.g. strips or grids). The reinforced soil block consists of the compact fill and reinforcing elements.Design Requirements
Design Criteria- The structures shall be designed for a minimum life of 100 years.
- The design loadings transferred from bridge abutments to the structures shall be specified on the Drawings. The live loading from the bridge approaches and the vertical and lateral loads from the earthwork shall be taken into account in the design.
- The structure shall satisfy the stability requirements of the AS 5100 for earth retaining structures.
- Allowable bearing pressures and settlements on the founding material under the reinforced soil block shall be determined by the designer from the geotechnical investigations.
- Drainage provisions shall be provided where necessary to intercept or divert groundwater and surface water to prevent scour or the development of hydrostatic pressure behind facing panels or saturation of any fill (approach and reinforced earth), and shall incorporate provisions to prevent saturation of the backfill in the event of a leaking water main. The drawings shall clearly show all drainage provisions.
- For straight walls the design shall provide for a 1 in 40 slope on the vertical wall face.
- If the design is to cater for future extensions (refer to the Project Design Brief or the Drawings), the design shall allow for both initial and future configurations. For walls which are to be extended in height, initially placed reinforcement and facing panels shall be designed to resist the future height wall and any surcharge without adjustment (except for removal of non standard capping panels). For walls that are to be extended laterally, the extension shall be able to be constructed without disturbing reinforcing straps that are to remain in place.
