Deadmen Retaining Wall in Construction: Function, Design & Installation
Retaining walls are vital in modern construction, serving to hold back soil, manage slopes, and prevent erosion. However, not all retaining walls can rely on gravity or cantilever strength alone—especially when dealing with tall structures, loose soil, or additional load from nearby buildings or vehicles. In these cases, deadmen (plural of “deadman”) are used to provide extra anchoring support, ensuring the wall’s long-term stability and safety.
In this article, we’ll explore the concept of deadmen retaining walls, their function, construction methods, advantages, and critical design considerations in modern construction projects.
What Is a Deadman in Retaining Wall Construction?
A deadman in retaining wall construction refers to a buried anchor, typically made of concrete, timber, or steel, that is connected to the wall using tiebacks (steel rods or cables). Its purpose is to resist lateral earth pressure that pushes against the retaining wall.
A deadmen retaining wall is a type of wall reinforced with one or more of these anchors to increase resistance to sliding, overturning, or structural failure. The deadmen act like “anchors in the earth,” buried deep behind the wall and counteracting the pressure coming from retained soil.
How Does a Deadmen Retaining Wall Work?
The function of a deadman system is based on physics: force resistance through tension and friction. When earth pressure pushes against a retaining wall, the deadman—buried far behind the wall and connected by a tie rod—resists that pressure by:
- Being anchored in stable soil further away from the wall.
- Using its mass and soil friction to stay in place.
- Transferring the force from the wall to the anchor through the tie rod.
This system increases the wall’s stability significantly, especially in poor soil conditions or when additional external loads are present.
Components of a Deadmen Retaining Wall
| Component | Description |
|---|---|
| Retaining Wall | The vertical structure retaining the earth. |
| Deadmen Anchors | Buried anchors (concrete blocks or timber) acting as anchors. |
| Tiebacks (Rods/Cables) | Steel elements connecting the wall and the deadman to transfer forces. |
| Anchor Plates | Steel or metal plates used to distribute force across tieback connections. |
| Compacted Soil | Soil surrounding the deadman that provides passive resistance. |
Where Are Deadmen Retaining Walls Used?
Deadmen anchors are not required for every retaining wall, but they are highly beneficial in the following conditions:
- Walls higher than 4 feet where lateral pressure increases significantly.
- Unstable soil conditions where the wall alone can’t resist sliding.
- Walls subjected to surcharge loads, such as nearby vehicles or buildings.
- Hillside or sloped terrain where natural gravitational pull works against the wall.
- Temporary construction works like shoring walls or trench boxes.
Types of Deadmen Used in Retaining Wall Systems
1. Concrete Deadmen
- Reinforced concrete blocks buried behind the wall.
- High durability and excellent for permanent structures.
2. Timber Deadmen
- Common in residential or light-duty applications.
- Made of pressure-treated timber beams.
3. Steel Deadmen
- Sometimes used in high-load or industrial applications.
- Can be combined with concrete for increased strength.
Design Considerations for Deadmen Retaining Walls
🔸 Deadman Size and Weight
The deadman’s size must be large enough to resist the expected pull from the tieback. This depends on:
- Wall height
- Soil conditions
- Applied loads (surcharge, water pressure)
🔸 Embedment Depth and Spacing
Deadmen are generally buried at least 3 to 6 feet deep and spaced every 4 to 8 feet along the wall.
🔸 Tieback Angle and Length
- Tiebacks should be installed at an angle (typically 15–45° downward from the horizontal).
- Must reach deep into stable soil and anchor fully into the deadman.
🔸 Soil Conditions
The frictional resistance between the soil and the deadman plays a major role in its effectiveness. Engineers must evaluate:
- Soil type (clay, sand, gravel)
- Moisture content
- Bearing capacity
Step-by-Step Installation Process
- Site Analysis & Design
Engineers assess load requirements and design the layout, number, and spacing of deadmen. - Excavation Behind the Wall
Trenches or pits are dug at the required depth and distance behind the wall. - Deadman Placement
Concrete blocks, timber beams, or steel anchors are placed perpendicular to the wall. - Tieback Installation
Galvanized steel rods or cables are installed, connecting the deadman to the retaining wall. - Anchor Plate Attachment
Metal plates are used to fasten tiebacks to both the wall and deadman. - Backfilling and Compaction
The area is backfilled and compacted in layers to enhance stability and minimize settlement. - Drainage Considerations
Drainage systems (e.g., gravel, weep holes) are installed to reduce hydrostatic pressure.
Table: Quick Overview of Deadmen Wall Design Parameters
| Design Element | Typical Value |
|---|---|
| Wall Height Supported | Up to 10–12 feet (with deadmen anchoring) |
| Deadman Spacing | Every 4–8 feet |
| Deadman Embedment | Minimum 3–6 feet |
| Tieback Diameter | ¾” to 1¼” galvanized steel rod/cable |
| Tieback Angle | 15° to 45° downward |
| Backfill Soil Type | Well-compacted granular soil preferred |
Benefits of Using Deadmen in Retaining Walls
✅ Enhanced Stability: Helps retain walls resist lateral earth pressure and prevent collapse.
✅ Cost-Effective Reinforcement: More affordable than overbuilding wall thickness or using geogrid systems.
✅ Versatile Applications: Works for various wall types—timber, block, poured concrete, or segmental.
✅ Simple Installation: Uses standard construction tools and materials.
✅ Long-Term Durability: Concrete and steel deadmen provide years of reliable service with minimal maintenance.
Limitations and Challenges
- Requires Space: Needs enough room behind the wall to place and embed the deadmen.
- Unsuitable for Confined Urban Sites: Not ideal where excavation space is limited.
- Dependent on Soil Strength: Not effective in extremely loose or saturated soils without soil stabilization.
- Potential for Corrosion: Tiebacks and plates need to be corrosion-resistant in damp or aggressive environments.
Conclusion
The deadmen retaining wall system is a proven, effective method for increasing the structural integrity of retaining walls under heavy loads or in challenging soil conditions. By anchoring the wall to stable ground behind it, deadmen provide passive resistance that helps maintain long-term wall stability.
Whether you’re managing hillside erosion, supporting a driveway, or designing a deep excavation, deadmen are a cost-effective and powerful solution when designed and installed correctly.
FAQs About Deadmen Retaining Walls
Q1. What is a deadman in a retaining wall?
A deadman is a buried anchor (concrete, timber, or steel) used to resist the lateral earth pressure acting on a retaining wall, connected via tiebacks.
Q2. How many deadmen are needed for a retaining wall?
It depends on the wall’s height and the soil pressure. Typically, deadmen are spaced every 4 to 8 feet.
Q3. Can I use timber instead of concrete for deadmen?
Yes, pressure-treated timber can be used for light-duty applications, but concrete is preferred for long-term or heavy-load conditions.
Q4. How deep should a deadman be buried?
Deadmen are usually buried 3 to 6 feet deep, or more, depending on the wall height and load.
Q5. Are deadmen needed for all retaining walls?
No. They’re mainly used when additional reinforcement is required—such as for taller walls or poor soil conditions.
Q6. Can I add deadmen to an existing retaining wall?
In some cases, yes—especially if the wall is showing signs of leaning or movement. However, retrofitting should be overseen by an engineer.
Q7. Do deadmen eliminate the need for drainage?
No. Even with deadmen, proper drainage is essential to relieve water pressure behind the wall.
