Technical News

Exclusively for Allan Block Design Professionals

June 2022

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ABU Online

Our Design Professional ABU Online events were created to help you with your retaining wall needs. Our local production and sales partners will be happy to schedule in person training on any topics you see below (call us if you are looking for those individuals) but feel free to use these to help with immediate needs.

training opportunities

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Submittals and AB Walls 3D+Terraces
6/16, 10/20

3D Modeling and AB Walls 3D+Terraces
6/23, 10/27

Water Management and AB Walls 3D+Terraces
6/30, 11/3

Best Practices for SRW Design
7/28, 11/10

AB Walls 3D+Terraces
7/21, 11/17

Segmental Retaining Wall Design

SRW Inspectors Presentation

SRW Architectural Presentation

Complex Composite Structures (CCS) and AB Walls 3D+Terraces

No-Fines Concrete and AB Walls

Terraces and Global Stability in AB Walls 3D+Terraces

AB Fence and Installation

Above Wall Considerations in AB Walls 3D+Terraces

Seismic Consideration in AB Walls

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Inspiring Project Ideas











In this Issue:

Multiple Tiers to Solution for the Whitefish Town Pump Station

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The town of Whitefish needed a new convenience store located at the entrance to town that would provide a "wow factor" and reflect the desired style of the area as a ‘Gateway to Whitefish’. The chosen site of the new convenience store had a significant grade change on the SE and East sides limiting space available for fueling stations. A terraced design with a more gradual change in elevation was desired and this project was the first to utilize the AB Walls 3D+Terraces design feature, allowing all sections of the terrace to be designed at the same time. The updates to the AB Walls software helped cut down on the design time.

AB Walls drawing

This project faced several complications during the construction process, but Dave Reynolds with Alpine Landscaping was able to use his experience and perseverance to meet and overcome each challenge. Despite the difficulties, the wall was completed by mid-2021 which allowed for the next phases of the construction to proceed, and the convenience store to open at the close of 2021. The addition of the Allan Block retaining wall not only helped functionally, by adding more fueling stations, but also met the town’s desire for a higher-end look when coming into town.

Check out the full case study in our entire case study library.

Tools: Designing Terraces in AB Walls with LEM

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Designing terraced retaining walls used to be a hassle, but with the latest update to our AB Walls Design Software, it has never been easier. When designing terraced retaining walls, the upper wall is treated as a surcharge on the lower wall design as standard practice. This method of designing terraced retaining walls, although correct, does not give design professionals the true impact of the upper wall on the lower wall for large walls. With the AB Walls update, instead of designing the individual wall with a surcharge, AB Walls can now design the wall as an entire terraced structure.

To offer design professionals the most accurate idea of the loading on their terraced structure, AB Walls was updated to include Limit Equilibrium methodology (LE) which utilizes the same calculation methods as a typical global stability analysis, except that it is limited to the wall design envelope. LEM uses a Simplified Method of Slices (Bishop’s Model) to determine the forward forces that need to be resisted by the geogrid layers and facing material. This allows the designer to make informed decisions about the geogrid being used as well as the stability of the structure. Although LEM gives us a better understanding of the internal loads, we want to stress that it does not replace a full global stability analysis, as it is only analyzing inside the wall envelope and not above and below the structure.

AB Walls LEM

Since LEM is based on geotechnical concepts, it has been accepted by the Federal Highway Administration (FHWA), American Association of State Highway and Transportation Officials (AASHTO), and the National Concrete Masonry Association (NCMA) as a viable alternative for traditional SRW internal design calculations. Download the FHWA published LEM manual (FHWA –HIF-17-004) or the Allan Block Engineering Manual to see a complete discussion on the Limit Equilibrium Method. Allan Block’s “Always Better” attitude is one reason why we have incorporated this more precise method directly in our design software AB Walls 3D+Terraces.

Engineer Talk: How to Handle Site Limitations

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It is not uncommon to have a project where a standard retaining wall design does not fit within the parameters of the site. Think about all the times when you would like to use an economical solution like Allan Block, but you have one or more of the following:

  • Utilities directly behind the wall in the reinforcement zone
  • Property lines close to the back of wall
  • Excavation limitations (Bedrock, existing structures above wall, etc.)
  • Fences above
  • Poor on site soils
  • High seismic conditions

Allan Block has multiple solutions to help you solve these tricky site limitations. The subsequent options are great alternative forms of reinforcement, with links to more detailed information.

Top of wall fence

While it may seem daunting to design retaining walls with difficult site conditions, Allan Block’s segmental retaining wall design software, AB Walls 3D+Terraces is a tool that can help provide the right information for you to make that engineered solution. The AB Walls 3D+Terraces Design Software can design SRW’s using NFC, Double Block Walls, as well as CCS.

If you have a project that has a limitation or have a complicated site, check out our AB Engineering Manual Chapter 7 for more information on CCS. We also provide weekly webinars or personal tutorials on how to apply these alternate forms of reinforcement in our AB Walls Design Software. Email us at to set one up.

Contractor Talk: The Importance of Surveying and Updating Plans

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How many times have you gone to your site and realized that the site plan you received doesn’t match the reality? Have you lost build time because the retaining wall or other structures were not laid out properly? Although surveying is only a part of the construction process it is very important to everything that comes after. This information is used by everyone during the construction process so any oversight or mistake will take time and money to resolve. The farther along the construction process, the greater the impact. These delays and change orders can greatly impact profit margins if the wall must be redesigned.

Surveying a jobsite

Benefits of proper surveying:

  • Ensure proper communication between design and construction teams
  • Identify and design for site limitations, i.e., water, utilities, etc.
  • Eliminate or reduce construction delays
  • Reduce change orders

For retaining walls, it is important to communicate where the wall is located. On most site civil plans, a simple line is used to represent the retaining walls. However, this does not tell the whole story. When surveying is done in the field and site staking is done for construction, it is critical to account for the wall setback or batter, along with communicating where the contractor will start wall construction. Therefore, are the stake representing the bottom of wall at the face or centerline and are offsets being provided?

To assist, Allan Block has developed a Pre-Construction Checklist that is also available within the AB Spec Book. This covers the different questions that should be asked and accounted for during the planning and surveying phase. Use this as a guide for the construction meeting to try and identify potential issues early and limit the impact on your profit.

Contact us at if you need preliminary assistance or give us a call at 800-899-5309 at ex. 3.

Hot Topic: SRW's Abut Existing Structures

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How do you design a modular retaining wall that adjoins an existing structure? Be it a building foundation, an existing concrete wall or even another segmental retaining wall (SRW) there are a few things to consider.

  • How are the walls abutting? Perpendicular or in-line?
  • The setback/batter of the walls – do they match?
  • How will they connect?

An SRW can abut an existing structure perpendicularly on its face with little concern beyond aesthetic but for wall abutting in-line, the concern of how the setback of the wall(s) will align come into consideration.

If the existing structure has no setback its thickness and height are factors that will affect the layout of the SRW. Sometimes the amount of setback could result in exposing the soil behind an existing retaining wall, which will require returns, either at the top or bottom of the SRW, to enclose the exposed soil.

Illustration of abutment Abutment example

It is not recommended to mechanically connect SRWs to existing structures for many reasons, as listed below.

  • SRWs are meant to move with soil movement and if they are connected to a rigid structure, the connection points will be subject to loading that was not designed for, resulting in damage to both structures.
  • If the existing structure is another SRW, the block heights and setbacks may not be the same which could lead to issues if the walls are to be weaved together. A solution would be to place a column between the 2 walls for a vertical transition.

If you have a SRW that is to adjoin with an existing structure, give the Allan Block engineering department a call (800-899-5309 x 3) or email for assistance.

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