Retaining wall blocks are extremely versatile and eco friendly. Ideal for applications such as landscaping, retaining cut and fill embankments, terracing, embankment and soil retention, construction of attenuation ponds as well as protection from soil erosion. Due to the diversity of the design of these retaining wall blocks, they allow for a variety of visual effects, suitable for domestic, industrial and commercial applications. Concrete block retaining walls are effective and extremely economical. They can be installed with spacing for plantability or as a closed structure. The interlocking method of construction make retaining wall blocks ideal for most retaining applications. A number of options, from plain smooth concrete to rock face with earthy colours which blend naturally into the environment are available. Steps may be incorporated into the walls:
What Are Gravity Retaining Walls
There are various types of these systems on the market with elevations ranging from open checkerboard appearance to closed vertical surface structure and many are plant supportive to varying degrees. Some systems are interlinked, while others interlock on the vertical and/or horizontal plane. All systems rely mostly on interblock friction to derive a measure of sliding resistance and under ideal conditions that is sufficient to prevent collapse when constructing a gravity retaining wall.
Yet, when substantial active lateral earth pressure occurs, considering the slender cross-section of these walls clearly no amount of interlocking or interlinking will prevent such a structure from collapsing. The most economical solution under such conditions is often found in constructing a multi-skin gravity retaining wall. Such a wall relies upon weight and frictional resistance to obtain stability. Alternatively, earth reinforcing or cement stabilised backfill techniques may be employed.
Light Gravity Walls
Light gravity retaining walls normally consist of a single skin of blocks and should not exceed a certain height limit. Please note that the NHBRC requirement is that one can build a wall to a height of 1.2m without consulting an engineer, but as a general rule 1.5m for walls no steeper than 70º is also possible. Any steeper and especially load-carrying walls must be designed by a qualified engineer, even if only 1.2m high.The planning of a plant supportive retaining wall should be looked at from the environmental point of view as well as considering structural and cost factors.
type of retaining system: Resist the temptation to specify slender, stretched-out types or imitations of proven blocks. The system should be chosen for maximum structural mass (no air voids within wall) combined with optimal rooting conditions. This will help in binding the system and embankment together.
Climatic conditions: Exposure to factors such as coastal, salt-laden winds, long hours of direct sunlight, deep shadows, etc., should be taken into account.
Function and type of vegetation: Herbaceous, deep rooting (low maintenance) or attractive flowers (high maintenance) may be considered. Mixed complimentary species or uniform ground covers can be planted. Feeding values for birds and insects must be investigated for a complete bio-engineering approach.
Heavy Gravity Walls
Heavy gravity walls are double skin walls, often with concrete reinforced backfill, for extra mass. A double skin, or layer, of blocks effectively doubles the gravity mass of the wall and increases the lever arm for overturning moments. The wall mass can be further increased by spacing the front and back skins using a stabilised fill and a geotextile or grid to hold the two faces in juxtaposition. It is not always necessary to take the second skin to the full height of the wall.
Often the designer is faced with a situation where the incline is steep and the mass of a wall system is insufficient to achieve a stable situation without resorting to additional measures. In most cases it will be found that the provision of a double skin wall for added mass is by far the cheapest solution, especially when it is not feasible to carry out additional excavation required to accommodate the installation of earth reinforcing techniques.
Factors influencing installation costs: as wall angles and heights increase so does cost. Due consideration has to be given to the presence of groundwater or unstable retained soil.