Engineering FAQ: Common Failures and Design Considerations
Avg. Read Time: 3 mins
In this Q&A, the Redi-Rock engineering team answers key questions to help you design Redi-Rock retaining walls confidently, especially in challenging environments like marine settings, detention basins, and expansive soils.
The Base Course
Short on time? Here are this article’s key takeaways…
- Redi-Rock engineers discuss four situations in which retaining walls can fail.
- Marine environments require integrated drainage to manage water pressure behind the wall.
- Retaining walls need free-draining backfill (e.g., ASTM 57 or 67 stone) to minimize hydrostatic pressure in detention basin applications.
- Expansive soils may need subgrade improvements - consult a local geotechnical engineer.
- Redi-Rock retaining walls are backed by extensive design resources and expert support to guide your project.
Frequently Asked Questions: Common Failures and Design Considerations
Designing reliable retaining wall systems starts with understanding common causes of failure. Equipping you with the knowledge and engineering insights to design better precast modular block walls.
- What is the most common reason retaining walls fail?
- What are important design considerations for building a Redi-Rock wall in a marine environment?
- What design considerations are needed when using a Redi-Rock wall in a detention basin?
- How do you prepare highly expansive soils for Redi-Rock?
- What design resources are available for Redi-Rock?
Redi-Rock Engineering Q & A
Q: What is the most common reason retaining walls fail?
A: Wall failures can result from poor drainage, site conditions like slopes above or below the wall, inadequate bearing capacity leading to excessive settlement, or construction issues such as improperly compacted backfill.
Q: What are important design considerations for building a Redi-Rock wall in a marine environment?
A: When Redi-Rock blocks are placed, they are not naturally watertight. Since Redi-Rock blocks are made of wet cast concrete and feature slower water absorption rates than traditional dry cast alternatives, water will escape through the cracks or relief joints. Therefore, it is best practice to include a drain within every wall. A drain provides a direct outlet for water to escape the wall, or trapped water can become impounded behind blocks, causing high pressure. We do not recommend installing waterproofing in a typical retaining wall scenario.
Q: What considerations are needed when using a Redi-Rock wall in a detention basin?
A: Proper retaining wall construction methods and materials, like free-draining stone, help mitigate long-term hydrostatic pressure. As a detention pond fills, water will get behind the wall. Redi-Rock blocks are not water-tight, and a drain is recommended. One of the best options for reducing the effect of having water and additional hydrostatic pressure behind the wall is to use a clean crushed, free-draining rock similar to ASTM 57 or 67 crushed stone, a three-quarter-inch or half-inch minus stone. As water fills up in front of the wall, so will the water behind the wall. Use free-draining rock to avoid excessive hydrostatic force on the back of the wall, which will allow water to leave quickly.
Q: How do you prepare highly expansive soils for Redi-Rock?
A: Follow the standard geotechnical practices in your area from your local geotechnical engineer. Precast modular block (PMB) walls like Redi-Rock are flexible retention systems, so they can handle some movement without compromising the wall's structure. Some additional excavation, compaction, or subgrade improvement may be required in highly expansive clay soils to protect the long-term performance of the completed wall.
Q: What design resources are available for Redi-Rock?
A: The Redi-Rock engineering page is home to everything you need to design critical wall structures. We invite you to explore the resources available to you, including:
- Preliminary Wall Sections
- Redi-Rock Wall + Wall Design Software
- SketchUp files
- Design Resource Manual
- Block Library
- Construction Details
- Specifications & Product Data
- Block & Application Test Reports
- Technical Resources for Barrier Walls
- Precast Modular Block Design Manual, Vol. 1 - Gravity Walls
- Engineering webinars and supplementary articles
Have more site-specific questions or need help refining your wall design? Connect with the Redi-Rock engineering team at engineering@redi-rock.com or (866)-222-8400, option 2. Or explore our full library of technical resources to move your project forward.