Deadman in Retaining Walls in Construction: Purpose, Design, and Installation

Retaining walls are vital structures in both residential and commercial construction, designed to hold back soil and prevent erosion or collapse on sloped terrains. As wall height increases or soil conditions become more complex, additional reinforcement is required. One of the most effective reinforcement techniques is the use of a deadman.

This article explores the concept of deadmen in retaining walls, detailing their function, types, design principles, installation procedures, and advantages within the context of construction.

What Is a Deadman in Retaining Walls?

In construction, a deadman is a buried anchor used to provide lateral support to a retaining wall. It is typically connected to the wall with tiebacks (rods, cables, or beams), anchoring the wall to a stable mass of soil behind it. The deadman resists the pressure from the soil retained by the wall, thereby enhancing the stability and longevity of the wall system.

The term “deadman” originates from the idea that the buried anchor acts as a static, immovable object that absorbs and resists loads without active movement.

Why Use a Deadman in Retaining Walls?

Retaining walls face constant pressure from the soil they are holding back, especially when the soil is wet or loose. A deadman adds resistance to that lateral pressure, which helps to:

• Prevent tilting or overturning
• Reduce wall displacement or failure
• Distribute soil pressure more evenly
• Reinforce taller retaining walls without increasing wall thickness

Deadmen are especially critical when:

• The wall exceeds 4 feet in height
• The backfill consists of loose or expansive soil
• There are surcharges from vehicles, structures, or slopes
• Drainage conditions are poor

How a Deadman Works in Retaining Walls

The deadman system works by transferring the lateral load from the wall to the buried anchor via tension elements (tiebacks). The mass of the deadman and the friction between it and the surrounding soil resist the movement of the wall.

Functional Overview:

1. The retaining wall experiences outward pressure from the soil.
2. Tiebacks attached to the wall extend into the soil and are anchored to the deadman.
3. As the wall attempts to move forward, the tiebacks pull on the deadman.
4. The deadman resists this force due to its embedment and weight, stabilizing the wall.

Types of Deadman Anchors Used in Retaining Walls

Key Components of a Deadman System

• Retaining Wall: The primary structure that holds back soil.
• Tieback or Rod: Connects the wall to the deadman and carries the load.
• Deadman Anchor: The buried mass that resists tension from the tieback.
• Backfill Soil: Compacted soil surrounding the deadman that provides frictional resistance.
• Anchor Plate (optional): Used to distribute force across a larger wall area.

Design Considerations for Deadman Systems

Proper planning and execution are critical to ensure a deadman system functions as intended. Here are some important design factors:

🔹 Placement and Depth

• Typically buried 6–10 feet behind the wall, depending on wall height.
• Should be below the frost line to avoid movement from freeze-thaw cycles.

🔹 Tieback Angle

• Installed horizontally or at a slight downward angle (10–15° is typical).
• Shall maintain direct line tension without sharp bends or deflections.

🔹 Deadman Size

• Varies based on expected load.
• A standard timber deadman might be 6×6 inches and 4–6 feet long.
• Concrete blocks might measure 2x2x4 feet or larger.

Installation Steps for a Deadman in a Retaining Wall

1. Excavate Wall and Deadman Trench
   • Dig behind the retaining wall where the deadman will be placed.
   • Ensure compacted, undisturbed soil at the deadman location.
2. Install Deadman Anchor
   • Position treated wood, concrete block, or steel plate at the required depth and orientation.
   • Use gravel or compacted backfill underneath for support.
3. Attach Tiebacks
   • Secure rods, cables, or beams from the deadman to the wall.
   • Ensure tension is correctly applied to counteract expected pressure.
4. Backfill and Compact
   • Backfill soil in layers, compacting thoroughly to eliminate voids.
   • Ensure moisture control to prevent settling or erosion.
5. Inspect and Reinforce
   • Check alignment, anchor integrity, and tension.
   • Repeat deadman installation as needed based on wall length and spacing.

Spacing Guidelines

• Deadmen are typically spaced every 6 to 8 feet along the retaining wall.
• Placement may vary depending on soil type, wall height, and surcharge conditions.

Advantages of Using Deadmen in Retaining Walls

✅ Structural Stability
Adds resistance to wall movement caused by soil pressure and moisture.

✅ Cost Efficiency
Allows use of thinner wall sections without compromising performance.

✅ Customizable
Flexible design that works with wood, block, or poured concrete walls.

✅ Ideal for Problematic Soils
Provides critical reinforcement in clay, sandy, or loose backfill conditions.

✅ Enhanced Load Capacity
Improves the wall’s ability to handle additional loads from above.

Limitations and Considerations

⚠️ Requires Sufficient Back Area
Deadmen need room behind the wall, making them unsuitable for tight property lines.

⚠️ Soil Conditions Must Support Anchors
Loose or poorly compacted soil may not provide adequate anchor resistance.

⚠️ Labor Intensive
Involves additional excavation, materials, and coordination.

⚠️ Drainage Still Critical
Deadmen won’t prevent wall failure due to water pressure—drainage systems are still essential.

Sample Layout Diagram (Text Format)

yamlCopyEdit   Retaining Wall
   | | | | | | | |
   | | | | | | | |
   | | | | | | | |
     |       |
     |------>|
  Tieback   Deadman Anchor
 (Rod/Cable)   (Concrete Block)
     |
     |        Compacted Soil
     |

Comparison Table: Gravity Wall vs. Wall with Deadman

Common Applications of Deadmen in Construction

• Residential garden walls exceeding 4 ft
• Commercial retaining structures
• Roadway embankment support
• Landscaping walls in hilly areas
• Seawalls and flood barrier systems

Conclusion

Deadmen are a simple but powerful engineering solution for stabilizing retaining walls. By extending the force resistance beyond the wall structure itself, they allow for stronger, more efficient wall designs, especially in challenging environments.

Whether using timber beams in a backyard landscaping project or concrete anchors for a highway retaining wall, deadman systems provide the necessary reinforcement to prevent movement, ensure safety, and prolong the wall’s life. Proper planning, quality materials, and adherence to engineering best practices are essential to getting the best results from a deadman installation.

FAQs About Deadman in Retaining Walls

Q1: What is a deadman in a retaining wall?

A deadman is a buried anchor—made of timber, concrete, or steel—used to stabilize a retaining wall by counteracting lateral soil pressure via tiebacks.

Q2: When should I use deadmen in my retaining wall?

Deadmen are typically used when walls exceed 4 feet in height, are in poor soil conditions, or bear additional loads from above.

Q3: How far back should a deadman be placed?

Usually, deadmen are installed 6 to 10 feet behind the retaining wall, depending on soil conditions and wall height.

Q4: What materials can be used for deadmen?

Common materials include treated wood beams, precast concrete blocks, and steel plate anchors.

Q5: Can I install deadmen myself?

Small-scale installations may be DIY-friendly, but professional consultation is recommended for structural walls or engineered systems.