While the retaining wall may have an aesthetic function, its main function is to support earth or the ground under which it sits. The main objective of this wall is therefore to allow sloping constructions and thus to avoid landslides.
Land pressure sometimes pushes to optimize space and therefore to build on sloping land. In this case, the retaining wall is the ideal solution.
A retaining wall is under strong pressure from the terrain it contains, which is why it cannot be built without respecting certain golden rules. If so, serious damage may occur.
8 golden rules for building a retaining wall
- Soil study
Before embarking on the construction of a retaining wall, a soil study should be carried out to determine the load that the soil can support.
The density of the soil is an important value to take into account because the thrust of the soil depends on it.
Knowing the angle of friction of the ground, although quite complex to determine, is also important since it provides the earth with its own stability.
This geotechnical study therefore makes it possible to determine the measurements of the retaining wall and thus to avoid future damage such as settlement or punching of the wall. Indeed, if the wall does not break, it can punch the ground downstream and tip over completely.
2. Design by a design office
The design of a retaining wall by a design office is strongly recommended, first of all because the study by qualified technicians makes it possible to size the structure correctly by preventing any risk of slipping and taking into account the overloads. .
Only a study carried out by an office of specialists makes it possible to know what stress can receive the ground by estimating the pressure of the grounds which will be contained by the wall of the wall. Thus, the design office will be able to give the optimal dimensions for the construction of a footing.
Find out what the pressure diagram looks like under a footing:
Rules for building a retaining wall
3. Properly made foundations
Particular care must be taken with the footings of the foundations. The latter makes it possible to transmit the thrust of the earth to the ground. In the event that this footing is not correctly made or balanced in the correct way, this can subsequently cause damage to the retaining wall.
In addition, as this structure is exposed to bad weather, it is necessary to think about burying the footings sufficiently to protect them from freezing. This depth is therefore dependent on the climate and the region in which the wall is built.
A properly made foundation also allows to ensure the abutment of the wall and prevent its sliding.
4. Quality of materials
The choice of materials is crucial when making the footing for the good performance of a retaining wall.
Reinforced concrete and breeze blocks are not equal, which is why when using breeze blocks, the panels must be squared with reinforced concrete chaining horizontally and vertically.
Whatever the final choice of material used, care should be taken to ensure that it is correctly made. In order for the retaining wall to be made efficiently, the concrete dosage must be correct and must be in a sufficient amount of reinforcement. In addition, the iron reinforcements must be arranged in accordance with the plan drawn up beforehand.
5. Efficient drainage system
Drainage through a retaining wall should be considered. The water must be able to drain properly. Indeed, if the water were to stagnate behind the wall, this would put additional pressure on the retaining wall on which cracks could be created.
The drainage system must be considered upstream of the construction of the retaining wall, and for this several systems can be considered:
Barbicans are very effective in quickly evacuating water and preventing the wall from rising in load during torrential rains,
A bed of cinder blocks mounted dry behind the wall also works very well in order to quickly evacuate the waters,
The drainage can be natural if the wall is built with draining materials (for example a dry stone wall will naturally allow the evacuation of water),
The Enkadrain product, an anti-vibration drainage geocomposite, has been very successful for several years now. This is explained by the fact that it is effective in both vertical and horizontal drainage. In addition, it is very resistant and has a filtering function in addition to being draining.
In addition to drainage along the wall, do not forget to provide drainage at the foot of the wall. The most used system is the draining sock: a pierced PVC pipe, surrounded by pebbles and all rolled up in a geotextile.
rule build retaining wall
6. Drainage quality of the backfill
In addition to the drainage system itself, the water must be able to circulate between the soil grains of the backfill. This is why the backfill located near the wall of the retaining wall must be draining.
It is therefore advisable to take an interest in the quality of the soil used for the backfill. If the local soil has draining properties, it is appropriate to use it and the addition of a geotextile before backfilling can also be considered. On the other hand, if the local soil does not have sufficient draining properties (which is the case, for example, with clay-type soil), it will be necessary to bring in exterior soil.
7. Waterproofing of the wall against the ground
In order to protect the steel reinforcements of a reinforced concrete wall, it is advisable to carry out a sealing layer on the back wall of the wall which is in contact with grounds and water.
8. Regular maintenance
The last golden rule to respect to have a robust and durable retaining wall concerns post-construction maintenance. Indeed, it is very important to ensure that the draining device does not clog over time, which can be the cause of many claims.
Not respecting these elementary rules of construction in the development of a retaining wall can lead to a lot of damage. In the field, our engineers unfortunately note that claims due to non-compliance with basic rules during the construction of retaining walls are frequent.
The disasters encountered on the retaining walls are, among others:
Cracks of varying sizes,
A movement of the wall that can lead to its collapse.
Depending on the quality of construction, the extent of the cracks and deformations can be very marked before the collapse of the wall. On the contrary, in some cases the wall suddenly collapses with few warning signs.
Reasons for damage to retaining walls
The primary reason for damage to a retaining wall is failure to follow basic rules during its construction.
Let’s find out the technical reasons that lead to poor construction of a retaining wall.
The total absence of calculation
Not carrying out a calculation before making a retaining wall is a mistake, because this type of work is complex and requires study.
Indeed, the pressure of the earth, the foundations of the wall, the reinforcement, the angle and the thickness of the retaining wall are very often poorly assessed without a measuring instrument. This is why it is advisable to make some calculations before embarking on the realization of the wall.