Retaining walls are solid wall constructions that hold soil lateral to a building to maintain the ground surface at different elevations on both sides. Retaining walls are indispensable because the soil at higher elevations tends to sink due to the various destabilising forces acting on it.

The primary purpose of retaining walls is to maintain the vertical or nearly vertical alignment of the soil or other materials destabilised by external forces. The different types of retaining walls are frequently utilised for a variety of purposes, including coastal engineering, irrigation engineering, and road, railway, and bridge construction. The base block is solidly monolithically linked to the vertical or inclined stem. Retaining walls are usually constructed to a height of 6 metres.

In this blog, we have covered the various functions and types of Retaining walls which are essential for the GATE CE, SSC JE CE and RRB JE Civil preparation.

Retaining Wall

A retaining wall is a structure designed to hold back soil and prevent erosion. Constructed from materials like concrete, stone, or timber, it's crucial in landscape engineering. Retaining walls prevent slope instability, create usable spaces, and enhance aesthetics. Proper design and engineering ensure safety and effectiveness against earth pressures.

Functions of Retaining Wall

The assorted functions of Retaining Walls encompass the following:

• The retaining wall acts as a barrier that prevents the movement of soil or other materials along a steep slope.
• They maintain the ground surface height by retaining the earth in place.
• Retaining walls that are made to withstand the soils or backfill securely transfer other externally applied stresses to a foundation.

Purpose of Retaining Wall

Retaining walls are essential structures used to support soil where level differences exist. Their main purpose is to prevent the natural movement of soil and maintain the shape of the terrain. In areas with steep slopes, retaining walls help protect against erosion, landslides, and slope failure.

They are widely used in construction to create flat surfaces on uneven ground, making space available for roads, buildings, and landscaping. In highway, railway, and irrigation projects, retaining walls help stabilize embankments and prevent soil from interfering with built structures. Apart from providing support, these walls also contribute to site safety and improve land usability in hilly or unstable areas.

Retaining walls are of different types on the basis of the type of building material used in their construction. The materials used can be wood, masonry block walls, stone, or concrete. The types of retaining walls are as follows:

Gravity Retaining Wall

• In a Gravity Retaining Wall, lateral earth pressure is resisted by the weight of the wall. Since the self-weight of the wall is the only resisting force in Gravity Retaining walls, these walls need a significant gravity load to resist the horizontal soil pressure.
• The forces of sliding, overturning, and bearing must be taken into account while constructing a gravity retaining wall, as they form the basis of the failure of the retaining wall. 
• It may be constructed from a variety of building materials, such as masonry units, concrete, and stone. 
• Gabion and crib retaining walls have become popular as common gravity retaining walls in recent years.

Reinforced Retaining Wall

In these walls, the stability against overturning is provided by the weight of the retaining wall. These are further classified into

Cantilever Retaining Wall

Fig 1: Cantilever Retaining Wall

• This wall is connected to the foundation and rests on the slab foundation.
• These walls can be constructed of RCC, prestressed concrete, or precast concrete. 
• This type of retaining wall is used for up to 10 metres.
• Stem and base slab are the two main components of the cantilever retaining wall. 
• Part of the base slab rests under the backfill material.
• Notably, the heel and the toe of the cantilever retaining walls are vertical.
• Compared to a gravity retaining wall, this retaining wall uses less concrete. 
• The failure in the cantilever retaining wall can occur by sliding, uplift pressure, and soil bearing pressure. The failure is also dependent on the various soil properties.

Counterfort Retaining Wall

Fig 2: Counterfort Retaining Wall

• These walls comprise counterforts, which are thin vertical concrete webs at regular intervals along the rear of the wall.
• These are used for heights greater than 8 metres.
• This counterfort connects the slab and the base together, acting monolithically with both. 
• The spacing between counterforts is more than one-half of the height.

Buttress Retaining Wall

Fig 3: Buttress Retaining Wall

• Buttress is a special type of counterfort retaining wall.
• These are constructed on the face of the wall rather than within the backfill. 
• They are not used due to the extra space occupied by buttresses.
• They are aesthetically inferior as compared to the cantilever retaining walls.

Gabion Retaining Wall

Fig 4: Gabion Retaining Wall

• These walls consist of gabions that are securely fastened to the wire and filled with stone.
• These retaining walls are inclined in the plan.
• Gabion Retaining walls are typically constructed of Stainless steel coated wires or galvanized steel wires. 
• These walls are generally used to present the erosion of roads, riverbanks, and other sloping locations.

Crib Retaining Wall

Fig 5: Crib Retaining Wall

• This wall consists of boxes of precast concrete that are interconnected with each other. 
• These precast boxes are filled with granular materials. These create a free-to-drain structure. 
• These subsume precast retaining walls and Timber retaining walls.
• This wall cannot be used to support earthen material along slopes.

Sheet Pile Retaining Wall

Fig 6: Sheet Pile Retaining Wall

• These are made up of interconnected piles penetrated into the foundation soil.
• Sheet piles may be of wood, steel, or precast concrete.
• The Sheet Pile retaining wall is stabilised by the earth pressure acting at the bottom of the retaining wall.

Anchored Retaining Wall

 Fig 7: Anchored Retaining Wall

• In this wall, the anchor resists soil pressure.
• The anchors generate resisting forces to oppose moments that may cause overturning and sliding of the wall.
• Notably, these anchors are loaded axially and can resist large loads.

Diaphragm Retaining Wall

Fig 8: Diaphragm Retaining Wall

• Diaphragm Retaining Wall consists of a fixed vertical RCC slab. 
• The earth pressure forces acting on the lower half of the wall stabilise the wall.

Design Considerations for Retaining Walls

When designing a retaining wall, several key factors must be considered to ensure structural safety and durability:

• Lateral Earth Pressure: The soil behind the wall exerts horizontal pressure that increases with height. The design must resist this pressure to prevent sliding, overturning, or failure.
• Backfill Material: The type, density, and moisture content of the backfill soil affect the pressure acting on the wall. Poorly compacted or expansive soils increase the load.
• Foundation Soil Strength: A strong foundation is essential to support the wall and resist settlement. Weak or loose foundation soil can lead to uneven pressure distribution and structural failure.
• Drainage Provisions: Water buildup behind the wall adds hydrostatic pressure. Weep holes, gravel filters, and drainage pipes must be included to release this pressure.
• Live Loads: Traffic, buildings, or equipment near the wall add extra loading, which must be factored into the design.
• Wall Height and Geometry: Taller walls face more pressure and require thicker sections and more reinforcement.
• Materials Used: The choice of construction material (e.g., RCC, stone, gabions) affects strength, cost, and durability.
• Slope and Site Topography: The natural angle of the site influences wall design. Steep slopes may need stepped or terraced walls.

Advantages of Retaining Wall

• Retaining walls can secure a structure in place.
• They help in retaining earth along the slope, thereby protecting the road and structures that lie beneath.
• These walls are designed to resist and oppose side gravity when your construction is positioned in an area with a slope. 
• They can help in the protection of landscaping from sinkhole damage.
• Retaining walls may improve the visual appeal of the surroundings.

Disadvantages of Retaining Wall

• Retaining walls may experience vertical fractures in the concrete due to extreme pressure.
• Foundation failure may be caused by soil pressure.
• Retaining walls made of Timber can be prone to termite attacks. 

Retaining Wall vs Boundary Wall

Retaining walls and boundary walls may appear similar in form, but their functions are entirely different. A retaining wall is built to resist the sideways pressure of soil and is a load-bearing structure, while a boundary wall mainly marks property limits and serves as a security or privacy barrier.

Retaining Wall Applications

Retaining walls have diverse applications in civil engineering and landscaping. They are used to prevent soil erosion, control slopes, and create usable spaces. Additionally, they serve as structural support for roads, bridges, and buildings, and contribute to flood control and aesthetic enhancement in various projects like terraced gardens, highways, and waterfront developments.

This article entailed all the necessary details regarding Retaining walls, their types, functions and various Advantages and Disadvantages. To attain excellence in assorted topics included in the syllabus of upcoming examinations, you should get enrolled in the AE/JE Civil Coaching and GATE Civil Coaching preparation. All of these courses are available on the Testbook App.

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