Precast concrete is a great option that offers several advantages to the builder. For example, for embankment containment works, a precast retaining wall
provides greater construction speed, as well as the possibility of entering service immediately after being installed.
There are many options for precast walls, but the ones that are frequently used in jobs where cuts and fillings are required are: reinforced earth walls, buttressed walls and screen walls. When selecting the best precast option for retaining walls, it is advisable to review various factors, such as:
• height of the wall
• type of soil
• desired slopes,
• required finish,
• handling equipment
• load to be sported
Reinforced Earth Walls
Reinforced earth walls are made up of a filling of granular material reinforced with tensors, which during the compaction process of the material are arranged in strips or layers and are connected to concrete slabs that make up the exterior of the wall.
The material is compacted to a density so that it achieves resistance and compressibility. Together with the tensioners, this ensures the stability of the ground. The tensioners can be metallic or plastic and are adhered to the ground by friction, developing the necessary tension to maintain the stability of the ground.
Among the advantages offered by reinforced earth walls are:
• The possibility of building large areas in a short time.
• Their installation can be made by small telescopic cranes.
• It is possible to raise reinforced earth walls using large-format masonry blocks with special geometry.
• They can have a smooth or bush hammered texture and a great diversity of colours/
• Great flexibility to achieve walls with curves of small radius and adaptability to different landscape conditions because they allow terraces with several levels.
These walls consist of a prefabricated screen system that can be vertical or inclined, to which some buttresses are left to increase the rigidity of the section and withstand the thrusts of the soil with the consequent decrease in the volume of concrete.
The prefabricated screens are joined with a footing cast on-site to create a monolithic set. These walls work in a similar way to a retaining wall cast on-site and are used to protect and stabilize slopes, as well as in abutments for bridges and on depressed roads.
Buttressed walls do not require much excavation, since the depth and dimensions of the footing can be reduced compared to that designed for a brick wall and can be designed of almost any height and width.
When this type of wall is used there is a considerable saving in concrete due to the lightening provided by the buttress system. Also, the volumes to be poured on-site are reduced.
In the same way as reinforced earth walls, the advantage of precast buttressed walls is that large areas can be built in a short time and installed with small telescopic cranes or with equipment for bridge construction and earthworks.
The screen wall is a structure composed of interlocking precast concrete crossbars that make up a box, the interior of which is filled with permeable granular soil to give it strength and mass. The floor-precast assembly behaves like a gravity wall so that when designing them the same considerations must be taken as for this type of wall, with the advantage of allowing tolerance of appreciable differential settlements.
The precasts are interconnected perpendicular and parallel to the surface of the slope to form a network capable of resisting earth pressure. The space between precasts is filled with granular material to allow water to flow freely between the crossbars, which can be made with different textures and colours, depending on the landscaping design.
The sieve walls allow plants to be planted between the precast, so that when the vegetation grows it covers the concrete and reveals a green slope.
Precast concrete retaining walls are a very interesting solution since they offer durability, versatility in construction and maintenance, use the soil for most of their volume and, thanks to the fact that they are produced in the plant, and guarantee very good quality.