Simply put, a retaining wall is a wall that sustains lateral soil pressure. It holds back water from entering the premises. For such a wall, there are major design considerations as a freestanding wall with no lateral support from the top cannot simply be built. The range of the dimensions of the retaining walls establishes the category of the structure.
There are 3 types of retaining wall structures:
1) Curbs: This type of retaining walls is the shortest of all the retaining structures. The structures underneath the soil are made depending on whether or not it is necessary to have a gutter in the lower side of the curb. The height of this structure is limited up to 0.6m above the ground level.
2) Short retaining walls: Walls as high as 3 m above the ground level belong to this category. They are made of a concrete masonry with uniform thickness and also has vertical wall reinforcing, and transverse footing. All this is done to make the wall able to bear the vertical weights of the wall, wall footing and earth fills.
3) Tall retaining walls: As the wall height increases, the wall design becomes more and more complex as the retaining wall design needs to be efficient enough to be able to handle the weight of a tall wall vertically. As the overturning moment increases sharply with the increase in the height, special care has to be taken to make it sturdier. One option is to construct a wall with tapering thickness. But, when the wall height becomes even taller, there is a need to consider various bracing techniques.
Design considerations apart from the wall height are:
• Basic loading: There is a loading on the retaining wall. The basic loading on the wall is considered as the sum of static earth pressure, water pressure, and pressure due to live loads. Generally, it is considered that the design pressure considered for retaining walls should not be less than 5 kilonewtons per cubic meter.
• Stability of the retaining wall itself: The wall built has to be strong enough to stand by itself and not crumble. This is usually done by using strong bonding power of concrete and bricks.
• Soil properties: apart from curbs, all other retaining walls are higher and so there is a need for estimating and analyzing the soil properties of the natural ground as well as the backfill. Attention should be given to factors like groundwater levels and soil porosity. Sometimes, design tests are performed on a sample of the soil to determine the properties.
• Earth pressure: The earth exerts pressure on the retaining structure. This pressure is strictly dependent on the lateral deformations that occur in the soil. Hence, the deformation conditions need to be estimated with reasonable accuracy. Thus one can make a rational prediction of the magnitude and distribution of earth pressure on the structure.
• Possible variations in the structure in future: When the area surrounding the retaining wall goes under construction as well, there is a possibility that some factors affecting the soil stability and loading may change. For example, there may be a need for additional surcharges or a need of removing the ground in front of the wall for building foundation purposes. Thus, possible effects of excavation processes on the wall bearing capacity should be kept in mind while constructing it itself.
• Fill slopes surrounding the retaining wall: There are some slopes formed naturally that are inadequately compacted. Such slope can possibly liquefy under adverse conditions like heavy rainfall, vibration or leakage. This results in a mud flow which can have serious consequences.
With all these considerations, it is possible to get a perfect retaining wall design. Thereby build a strong and sturdy retaining wall that can withstand the attacks of nature.