Retaining Wall Design and its types used in construction

Retaining Wall designs are the vertical or near-vertical structures that are designed to make level areas on the sloping sites. This type of wall designs is used in geotechnical engineering with the purpose of reinforcing soils, enhancing the bearing capacity, and also enhancing the resistance of soils to different settlements.

Figure 1: Retaining Wall designs

Purpose of Retaining Walls

Retaining walls are used with the aim of providing additional support to the natural slopes which are at risk of failure by creating levels on the sloping areas. Retaining wall designs are used to maximize the development spaces and create terraces to run along the slopes. This type of wall design is also used to form the basement walls, metro stations, and car parking areas underground in cities and towns.

How does it work in the construction units?

It is designed to restrain the soil in the construction sites at an angle steeper. At this angle, this type of wall design can be held naturally without the chance of failing.

These walls are constructed to hold back the soil materials or withstand lateral pressure. This lateral pressure could occur due to the liquid pressure, earth filling, sand, or the presence of other granular materials behind the structure of the retaining walls. The lateral earth pressur has been exerted by the base of the walls as the backfill is deeper and the vertical stress is higher.

Types of Retaining Walls

Different types of retaining walls are available in different shapes and sizes which are used for different goals. These types include:

Gravity Retaining Wall

In a Gravity retaining wall, the gravitational forces of their own weight have been used which helps to resist the lateral earth pressure that comes from the soil behind the walls. This helps to prevent the sliding and toppling which is caused by the lateral earth pressure. These gravity walls are easy to build and able to retain heights up to 3m but it is not suitable for retained heights above 3m. In the case of building any higher walls, the retaining structure takes too much space and becomes too heavy for the ground which leads to bearing capacity failure.

Figure 2: Gravity retaining wall

Gabion Retaining Walls

These types of walls are multi-celled, rectangular wire mesh boxes. These walls are filled with rocks and other materials which are suitable for this wall.

This Gabion wall is used in the erosion control structures’s constructions. This type of retaining wall is also used for the stabilization of the steep slopes.

Figure 3: Gabion Walls

Cantilever Retaining Wall

These types of retaining walls are built to use reinforced concrete with an inverted T-shaped or L-shaped foundation. A stem and a base slab are part of this retaining wall design which is situated under the backfill. The vertical stress of this wall has been transferred to the foundation of the wall which helps to prevent the toppling due to the lateral earth pressure. Thus, this cantilever wall is allowed to stand unobstructed. The t-shaped foundation that is used in this wall helps to provide further stability to the retaining wall structure. This type of wall takes little space and is also suitable for retained heights which is up to 5m.

Figure 4: Cantilever Retaining Wall

Crib Retaining Wall

Crib walls are the form of gravity walls which are constructed of interlocking individual boxes. These boxes are made from pre-cast concrete and timbers and filled with crushed stones or coarse granular materials which helps to create a free-draining structure. These retaining walls are used to support planter areas but are not suitable for slopes.

Figure 5: Crib Wall

Counter-fort Retaining Wall

The counter-fort wall is the form of a cantilever retaining wall, but in this case, walls are strengthened with counterforts along with the back of the base slab and wall slab. The spacing of this wall is equal to or sometimes slightly larger than half of the height of this wall.

Figure 6: Counter-fort Wall

Anchored Retaining Wall

In case of limited space available or there is a requirement for thin retaining walls, an Anchored retaining wall is used. These Anchored walls are suitable for loose soils that are over rocks. These walls are able to act against overturning or sliding pressures. This type of wall structure system can be used to construct high retaining walls.

Figure 7: Anchored retaining wall

Piled Retaining Wall

Reinforced concrete piles are adjusted to each other to form pile retaining wall structures. These walls are used for both temporary and permanent construction works. High-stiffness retaining elements have been offered by these walls. These elements help to hold the lateral pressure in large excavation depths. Steel sheets are used to build sheet piles into the excavations or a slope up to a required depth. Sheet piles are not able to resist very high pressure. It is economical till the height of 6m.

Figure 8: Piled Retaining Wall

Hybrid Systems

This hybrid system uses both reinforcement and mass to achieve stability. This hybrid system is also known as Composite retaining wall systems.

Figure 9: Hybrid retaining wall system

To learn more, watch the following video tutorial.

Video Source: Brendan Hasty

Mechanically Stabilized Earth Retaining wall

This is the most commonly used and most economical constructed retaining wall.

These types of walls have been supported by the selected fills and can be held by reinforcements. These mechanically stabilized earth walls include temporary earth retaining walls, panels, or concrete blocks.

Figure 10: Mechanically stabilized earth wall