What is a Retaining Wall?
Retaining walls are structures designed to retain large bodies of soil at a given height. They are used in many applications across the construction industry, from small-scale landscaping projects to large infrastructure developments.
They are essential in areas where the natural ground level has been modified or on slopes requiring excavations. They must be designed to effectively withstand the horizontal pressure from the retained wall and groundwater, which is driven by gravity and pushes downwards and outwards.
Where Are Retaining Walls Used?
Due to their incredible versatility, retaining walls may be used in several applications. Some of their most common uses include:
Basements: Retaining walls can stabilise the soil around basements, preventing inward movement and protecting the building’s walls from horizontal soil pressure, which could lead to the collapse of the building’s internal walls.
Landscaping and Outdoor Spaces: Retaining walls are commonly used to support garden walls, outdoor staircases, and raised footpaths. Similarly, they can also serve as structural walls for swimming pools.
Hilly Areas for Buildings and Infrastructure Projects: Infrastructure such as roads, highways, bridges, railways, and buildings on uneven terrain often requires retaining walls to prevent soil from adjacent slopes from encroaching and to stabilise the underlying ground, preventing settlement or sinking.
The Role of Engineers in Retaining Wall Design
Retaining walls are designed by structural and civil engineers who are responsible for specifying the wall’s dimensions, materials, and any necessary reinforcement/strengthening. Some of the key considerations engineers make in retaining wall design include:
- Site constraints that may limit accessibility for machinery and personnel, including confined spaces and proximity to existing structures.
- The required load-bearing capacity to retain the soil is critical in determining the type of retaining wall and the materials used in its construction.
- Aesthetic considerations: how will the wall be integrated into the surrounding landscape?
- Budget constraints
- Environmental factors: groundwater levels, erosion risks, and soil stability are some factors engineers must consider when designing a retaining wall.
- Ground Conditions: On larger, more variable projects, engineers often conduct detailed site investigations to assess the soil type and its properties to help optimise the cost-effectiveness of the final retaining wall design. In these cases, soil samples collected from the site are tested in laboratories to evaluate:
- Soil Density
- Cohesive Strength
- Friction Angle (Assessing how steep a soil sample can be stacked before it collapses)
These factors help structural engineers calculate the pressure exerted on the retaining wall and ensure its stability under various load-bearing conditions.
Types of Retaining Walls
The selection of the appropriate retaining wall depends on many factors, including the height of the retained soil, ground conditions, and the site location. Some of the most common types of retaining walls include:
Gravity-Retaining Walls: These usually have a trapezoidal shape and rely on their weight and thickness to resist soil pressure.
Cantilever Retaining Walls: Similar to gravity retaining walls, they incorporate a base slab that extends into the soil, providing additional resistance against overturning.
Piled Retaining Walls: Made from steel or reinforced concrete piles driven deep into the ground to counteract horizontal soil pressure in the retained area.
Anchored Retaining Walls: Here, cables or rods act like anchors, tying the wall back into the soil to resist horizontal forces.
Reinforced Soil Walls (also known as Mechanically Stabilized Earth Walls): These walls are constructed from reclaimed or engineered fill, which is reinforced with metallic strips or plastic meshes.
For more information about the technical side of retaining wall design, please refer to the attached PDF. This E-Guide details the advantages and disadvantages of the most commonly used retaining walls, how they work, and how they can be strengthened.
At Harban Redwood, our experienced structural engineers understand which retaining walls work best for each building project. After finalising the design, we collaborate closely with homeowners, architects, builders, and steel fabricators to ensure the structural systems are stable, facilitate seamless construction and deliver an aesthetically pleasing result.
For more information from an expert retaining wall engineer, Banbury, today, email us at info@harbanredwood.com to learn more about the solutions for creating lasting reinforcement.
