Deadman Retaining Wall in Construction: Function, Design, and Benefits
Retaining walls are essential structural systems used to resist soil pressure and hold back earth in landscapes, infrastructure, and building sites. As the height or load on a retaining wall increases, so does the pressure it must resist. To enhance their structural integrity, one of the most effective and time-tested reinforcement techniques is the use of deadman anchors—leading to what’s commonly referred to as a deadman retaining wall.
This article explains what a deadman retaining wall is, how it works, when it’s needed, how it’s designed and constructed, and why it plays a crucial role in modern construction projects.
What Is a Deadman Retaining Wall?
A deadman retaining wall is a type of reinforced retaining wall that includes buried anchors, known as deadmen, which are connected to the wall using tiebacks. These buried elements resist the outward force exerted by the soil retained by the wall, improving stability and preventing tipping or collapse.
The term “deadman” comes from the concept that the buried anchor is static and immovable, much like a dead weight, resisting movement through its own mass and the friction with the surrounding soil.
Why Use a Deadman System in Retaining Walls?
As retaining walls get taller or are subjected to more pressure (due to backfill weight, slopes, or additional loads like structures or vehicles), the risk of structural failure increases. A deadman system provides critical tensile reinforcement behind the wall, offering several benefits:
- Prevents wall tilting or sliding
- Increases wall height capacity without increasing wall thickness
- Reduces material costs
- Improves long-term durability and structural performance
Deadman systems are especially useful for:
- Walls taller than 4 feet
- Projects with limited room in front of the wall
- Poor soil conditions or expansive clays
- Heavy surcharge loads near the wall
How a Deadman Retaining Wall Works
The retaining wall holds back soil using vertical resistance. However, over time, horizontal forces from the backfill can cause it to bulge or lean outward. The deadman acts as a counterbalance to these forces.
Here’s how it works:
- Tiebacks or rods are attached to the back of the wall and extend into the soil.
- The tiebacks are connected to deadman anchors buried deeper into stable soil.
- When the wall is pushed outward by soil pressure, the tiebacks pull against the deadman, which resists movement due to its mass and embedment.
- The system creates a force equilibrium—stopping or reducing wall deflection.
Components of a Deadman Retaining Wall
| Component | Description |
|---|---|
| Retaining Wall | The visible structure that holds back soil. |
| Deadman Anchor | A buried element (usually wood, concrete, or steel) that serves as the anchor. |
| Tieback | The connection (rod, cable, or timber) between the wall and deadman anchor. |
| Backfill | The compacted soil placed behind the wall and around the deadman. |
| Drainage System | Keeps water from building up behind the wall and increasing pressure. |
Deadman Types Used in Retaining Walls
| Deadman Type | Material | Best For |
|---|---|---|
| Timber Deadman | Pressure-treated wood | Residential or light-duty timber walls |
| Concrete Block Deadman | Precast or cast-in-place | Medium to heavy-duty retaining walls |
| Steel Plate Anchor | Steel plates with tieback rods | High-load applications or engineered systems |
Design Guidelines for Deadman Retaining Walls
Designing a deadman retaining wall involves a careful evaluation of site conditions, soil characteristics, and load expectations. Key factors include:
🔸 Spacing
- Typically every 6 to 8 feet along the length of the wall.
🔸 Depth
- Deadman anchors should be buried 3 to 6 feet behind the wall depending on the wall height and load.
🔸 Size
- Timber deadmen: 6×6 or 8×8 inches, 4 to 6 feet long
- Concrete deadmen: 2x2x4 ft blocks or larger depending on force requirements
🔸 Angle of Tieback
- Tiebacks are usually installed horizontal or slightly downward (5–15° downward angle) to improve anchoring effectiveness.
Installation Steps for Deadman Retaining Wall
- Excavation
- Dig the trench for the wall and additional trenches behind the wall where deadmen will be buried.
- Wall Construction
- Build the retaining wall up to the desired height using block, concrete, or timber.
- Deadman Placement
- Install the deadman anchors (wood beams, concrete blocks, etc.) in the trenches at the correct spacing and depth.
- Tieback Connection
- Connect tiebacks between the retaining wall and deadmen. Secure tightly to prevent slack.
- Backfilling and Compaction
- Refill the area with soil in compacted layers to reduce settlement and enhance deadman resistance.
- Drainage Installation
- Place weep holes, drainage pipes, or gravel backfill to reduce hydrostatic pressure.
Visual Layout (Text Format)
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[Deadman] [Deadman] [Deadman]
Table: Gravity Wall vs. Deadman Retaining Wall
| Aspect | Gravity Retaining Wall | Deadman Retaining Wall |
|---|---|---|
| Wall Thickness | Thick and heavy | Slimmer, relies on anchors |
| Height Limitations | Up to 4 ft (without reinforcement) | 4+ ft with proper deadman reinforcement |
| Soil Pressure Resistance | Relies on wall mass | Resists pressure through tiebacks and deadmen |
| Installation Complexity | Easier, but material-heavy | More complex, but efficient for taller walls |
| Cost | Higher material cost | Lower wall cost but requires anchor installation |
Advantages of Using Deadmen in Retaining Walls
✅ Increased Stability
Provides resistance to overturning and sliding, particularly in tall or heavily loaded walls.
✅ Material Savings
Reduces the need for excessively thick or heavy wall materials.
✅ Adaptable
Can be used with timber, masonry, concrete, or segmental block walls.
✅ Effective in Poor Soil Conditions
Works well in sandy or loose soils where standard retaining methods fail.
✅ Proven Engineering Solution
Deadman anchoring has been successfully used in both modern and traditional construction.
Disadvantages and Considerations
⚠️ Requires Rear Space
Needs 3–6 feet of space behind the wall—limiting use in tight boundaries.
⚠️ Labor and Excavation
Involves more digging and complexity than standard wall construction.
⚠️ Needs Proper Drainage
Water buildup can increase load and reduce effectiveness of the deadman system.
Applications of Deadman Retaining Walls
- Residential landscape walls exceeding 4 ft
- Commercial retaining walls along roadways or buildings
- Hillside or sloped terrain stabilization
- Erosion control walls near water bodies
- Retaining structures in flood-prone areas
Best Practices for Deadman Retaining Walls
- Use pressure-treated wood to prevent rot if using timber deadmen.
- Compact soil thoroughly around deadmen to maximize friction and hold.
- Include adequate drainage to reduce hydrostatic pressure buildup.
- Space deadmen evenly and double up if walls are very tall or heavily loaded.
- Always consult with an engineer for large-scale or critical walls.
Conclusion
A deadman retaining wall is an effective and economical solution for building stable, high-performance retaining systems in challenging conditions. By using buried anchors (deadmen) tied back to the wall, this technique adds a powerful layer of reinforcement that protects against wall failure due to soil pressure, water load, or surcharges.
Though it requires more planning and space than basic wall types, the added safety, longevity, and flexibility make deadman systems ideal for both residential and commercial applications—especially where conditions demand more than just gravity and mass.
FAQs About Deadman Retaining Wall
Q1: What is a deadman in retaining wall construction?
A deadman is a buried anchor placed behind a retaining wall, connected by a tieback. It provides additional resistance to lateral soil pressure.
Q2: How far apart should deadmen be placed?
Typically, deadmen are spaced 6 to 8 feet apart depending on wall height, load, and soil conditions.
Q3: What materials can be used as deadmen?
Deadmen can be made from treated wood beams, concrete blocks, or steel plates, depending on the load requirements and soil type.
Q4: Can I install a deadman retaining wall myself?
For small walls, yes—with proper tools and understanding. For walls over 4 feet or under heavy load, it’s best to consult an engineer.
