The Lord Shaughnessy building is a residential housing complex in Vancouver, BC. Originally built in 1980, the owners were looking to provide some updated aesthetics to the exterior. For this, the owners turned to LADR Landscapes and Ryzuk Engineering, who are both companies in Victoria, BC, to create an updated exterior design.

The building uses a below ground parking lot for its residents. This was an existing structure they were looking to enhance the design around. The owners were looking to improve upon the walkways and stairs and provide additional patio and usable open space for its residents. To create this, LADR called for a retaining wall surrounding the property. To meet the desired aesthetics, they specified Allan Block to be provided by Expocrete Concrete Products. However, with the limited room for installation and the need for usable space, it did not seem that a standard geogrid reinforced wall would be a viable option.

This was a perfect application for no-fines concrete. With roughly an 8ft (2.4m) height along much of the wall, a typical geogrid reinforced design would require a minimum grid length of 5 ft (1.5m). With an additional offset of about 1ft (0.3m), the overall structure depth would have been a minimum of 6ft (1.8m). In utilizing a no-fines concrete (NFC) design, both the excavation and infill were limited to a fractional 3ft (0.9m) behind the new wall facing. Being that the new wall was to act primarily as a facing, the NFC was also used as a means to adhere the new wall to the existing concrete structure already running along the edge of the property.

The Lord Shaughnessy retaining wall was also a first for Anthony Sampson and his team at Set In Stone Construction. Anthony had previously completed the AB Contractor Certification Course before this project, and was well equipped to handle his first segmental retaining wall (SRW) project. Although he had never installed an NFC or Allan Block wall before, he told us, “The project ran quite smoothly and there wasn't any real issues”. Anthony worked with Island Diversified Concrete to supply the NFC for the job. The Set In Stone Construction team, along with assistance from Expocrete and the designs from both LADR Landscapes and Ryzuk Engineering, made the project a success. The updated exterior, the new patio space, and the renovated stairs and walkways to the underground parking lot looked phenomenal and provided the perfect outdoor accent for the Lord Shaughnessy complex.

See the full case study and more images here.

Allan Block’s design software, AB Walls 3D+Terraces, has been helping engineers design Allan Block segmental retaining walls since 1996. Among its many functions is the ability to design walls using no-fines concrete (NFC). As we have been discussing, NFC effectively increases the effective friction angle of the backfill and builds a permanent cohesion into the NFC mass, and designing with it is remarkably straight forward. In one approach for reviewing external stability, using NFC as backfill simply creates a deeper wall thickness, which in turn creates a larger mass to resist sliding and overturning forces. To follow a more geotechnical design approach we had shear tests conducted on NFC to provide the designer the required properties of the soil to conduct a proper design review. Refer to the Tech sheet on NFC testing to learn more about understanding the process and the results of the tests. Through this testing we have established a friction angle for the NFC which allows not only an external analysis, but by using the methodology referred to as Internal Compound Stability, an internal analysis may also be performed to ensure that the structure will hold together.

Typical geogrid reinforced walls rely on the grid to work together with the facing and compacted soil, forming a composite mass to resist sliding and overturning forces. Engineers designing geogrid walls must not only analyze the external stability, but the internal stability of the structure. Internal stability looks at grid strength, grid length and grid spacing, and can be complicated by large surcharges or slopes above. When designing with NFC, the wet concrete aggregate mix is placed within the cores of each block and behind the block. When solidified, it effectively creates a deeper and heavier gravity wall. See the Construction Considerations for No-Fines Concrete article in this newsletter for tips on building walls with NFC.

When designing an NFC wall, the designer must evaluate the external stability of the wall, sliding, overturning, and bearing. However, internal analysis is not necessary. Those calculations are specific to geogrid reinforced structures where you evaluate grid spacing, grid strength, block/grid connection, and geogrid soil pullout capacity. For an expanded look into designing with NFC, please review our Design Tech Sheet on the topic.

The NFC mass, which includes the Allan Block facing, has a much shallower structure depth than a geogrid reinforced wall. Therefore, it can be perfect for areas on sites that have tight construction restraints, such as closeness to property lines or possibly existing utilities. NFC can also be used for complex structures where there might be a bedrock ledge or other obstruction that cannot be moved. Using the Complex Composite Structure (CCS) functions within AB Walls, a designer could have a wall that has a shorter section of NFC below a deeper geogrid section as shown here. You can read more about the CCS functions in Chapter Seven in the Allan Block Engineering Manual.

AB Walls can do it all for you, for more than 30 years, it continues to expand its capabilities and the newest version - AB Walls 3D+Terraces was expanded to include the ability design terraced structures. For more information on AB Walls 3D+Terraces or to request a copy, see our website or contact us directly at engineering@allanblock.com.

As you have heard, this is not a new concept. No-fines concrete was created in the 1800’s and has been used with SRW and AB Walls for over 25 years. We generally like to refer to it as “stabilized backfill” since that is exactly how it works. Regarding how it is installed, you need to think of it more as granular material coated with Portland cement and less like concrete.

How do you mix it? There are many ways to mix NFC. Depending on the size, complexity, and access to the site, you may employ the use of a ready-mix truck directly from a local plant, use a portable on-site concrete mixer, or a ribbon mixer attachment on a skid steer. However your NFC is mixed, the next step is getting it to the wall.

How do you place it within the wall? It cannot be pumped, so the most common way to transport the NFC mix is in the bucket of your skid steer. This will allow you to transport a large quantity to even the most difficult wall locations on site. Ultimately, each site will dictate the most effective mixing and transportation option that will be the most cost effective for your project.

How do you install it? Refer to the AB Commercial Installation Manual for the complete installation steps when preparing the base trench and installing the first course of blocks. Once the first course of is installed and leveled, follow these simple steps to place the no-fines concrete Backfill:

• It is recommended that for straight retaining wall sections, one of the back wings of the Allan Block units is removed to help secure the block face to the concrete backfill.
• The vertical height of a pour should not exceed 16 inches (405 mm) or two courses of block.
• Additional pours can be made as soon as the no-fines concrete backfill in the previous lift has set, which is usually not longer than 2 to 3 hours. Additional courses of block could be stacked while waiting for the backfill to cure.

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We all know that designing a retaining wall is a lot more complicated than just stacking blocks, and few engineers know that more than this quarter’s designer spotlight – Josh Lyon with Klober Engineering Services out of Springfield, Tennessee. Josh is one of the top engineers designing Allan Block Walls and we believe that every designer could learn a thing or two from him.

Josh graduated in 2004 and was immediately hired at Klober Engineering where he started his engineering design career. Josh enjoyed the small firm environment and family-like appeal of the company, and still does to this day. In 2007 they began including retaining wall designs into their wheelhouse, and that is where Allan Block came into the story. Allan Block was quick to get Josh a copy of our AB Walls Design Software, and Klober has been completing in-house designs ever since. The segmental retaining wall (SRW) market was still relatively new in the Springfield area and because of their early involvement, retaining walls became somewhat of a niche role for Klober. Josh says that because of the efficiency of the AB Walls software and top-notch engineering support, he is always promoting Allan Block.

Josh and the other designers at Klober Engineering Services always go above and beyond when it comes to retaining wall design. They always make sure to pay very close attention to every project that comes across their desk, looking for any conflicting information on the plans. If there is ever anything that is not clear, Josh makes sure to call the site civil to clarify what is intended and never assume. It is small steps like this that set Klober Engineering apart, and it is something that all designers could learn to do. Because of his attention to detail, Josh is never intimidated by projects and loves working on difficult and unique challenges. Often times this means working with developers to push as much usable land into the site as possible, but sometimes it means talking to a homeowner to really understand the exact aesthetic they are looking for to create their dream back yard.

Josh is always up for a challenging project and has the engineering experience to make sure it will be designed with Best Practices in mind. He strives to keep his customers happy by providing high-quality work on every single project no matter the size. We cannot thank him enough for setting such an amazing example of what it means to be a top Allan Block designer, and we are excited to see all of the amazing walls that he designs in the future. Thank you very much, Josh.