July 17, 2018

Best Practices for Zero Retaining Wall Failures - Initial Grid Location & Maximum Grid Spacing


For a segmental retaining wall to be properly reinforced, grid placement is key.

The first layer of geogrid should be placed on top of the base course of block. This way the geogrid starts at the bottom of the wall where the most pressure exists.  Beyond this point, 2 course spacing or 16 in (40 cm) maximum spacing provides the best overall performance of the reinforced structure.

Some applications, including tall walls, might require single course spacing for part or all of the wall height. 
 (ref. BP, Chapter 2.10 & 11)

Allan Block is working to achieve our industry initiative of Zero Wall Failures. With our Best Practices Manual and experience in the industry we are trying to expand the knowledge base for the design of segmental retaining walls (SRW's) by communicating and educating the professionals in the industry.  To see the full Best Practices Manual, visit allanblock.com to download today and keep an eye out for more industry Best Practice recommendations here.
 



July 12, 2018

Best Practices for Zero Retaining Wall Failures - Minimum Grid Lengths


Segmental retaining walls are built everyday where many are tall enough that they require reinforcement.  The most common type of reinforcement is called geogrid.  Geogrid is rolled out behind the wall at block course intervals, and should be a minimum of 60% of total wall height measured from the top of the base to the top of the top wall block. 

Some applications, especially those with poor soil, may require geogrid layers to be significantly longer than 60% of the wall height.  If you are unsure how to properly reinforce your wall, be sure to contact one of the Allan Block engineers @ (800) 899-5309 ext. 3    (ref. BP, Chapter 2.9)

Allan Block is working to achieve our industry initiative of Zero Wall Failures. With our Best Practices Manual and experience in the industry we are trying to expand the knowledge base for the design of segmental retaining walls (SRW's) by communicating and educating the professionals in the industry.  To see the full Best Practices Manual, visit allanblock.com to download today and keep an eye out for more industry Best Practice recommendations here.

July 10, 2018

Best Practices for Zero Retaining Wall Failures - Base Trench Considerations


When constructing a base for a segmental retaining wall similar to Allan Block, it is typical to use wall rock for base material. For more information on wall rock see Chapter 2, Section 2.4.  The base should be 12 in. (30 cm) wider than the block depth.  Therefore, the base is typically 6 in (15 cm) deep by 24 in (60 cm). A larger base may be required for poor foundation soils.  The wall unit should be centered on the base.

For deeper facing units such as AB Fieldstone, which creates a unit about 24 in. (60 cm) deep with the Long Anchoring unit (LAU), the typical base width would be 36 in (90 cm).

For walls with a deeper than typical minimum sized base, it is common to add a continuous longitudinal layer of geogrid, 3 in (7.5 cm) to 6 in (15 cm) above the bottom of the trench. This geogrid provides additional stability to the compacted base and helps to span lesser quality soils.   (ref. BP, Chapter 2.8)

Allan Block is working to achieve our industry initiative of Zero Wall Failures. With our Best Practices Manual and experience in the industry we are trying to expand the knowledge base for the design of segmental retaining walls (SRW's) by communicating and educating the professionals in the industry.  To see the full Best Practices Manual, visit allanblock.com to download today and keep an eye out for more industry Best Practice recommendations here.

June 28, 2018

Best Practices for Zero Retaining Wall Failures - Base Trench Requirements



A proper base is essential for the stability of a segmental retaining wall similar to Allan Block. Typical depth of the trench is based on a minimum 6 in (15 cm) deep compacted wall rock base and buried block depth equal to 1 in (2.5 cm) of depth per foot (30 cm) of wall height.

If there are slopes below the wall, a deeper base trench may be necessary.

The base trench should be compacted to the level specified in the geotechnical report and inspected by the on-site soils engineer prior to any base material being placed. (ref. BP, Chapter 2.7)

Allan Block is working to achieve our industry initiative of Zero Wall Failures. With our Best Practices Manual and experience in the industry we are trying to expand the knowledge base for the design of segmental retaining walls (SRW's) by communicating and educating the professionals in the industry.  To see the full Best Practices Manual, visit allanblock.com to download today and keep an eye out for more industry Best Practice recommendations here.

June 26, 2018

Best Practices for Zero Retaining Wall Failures - Soil Parameter Verification


Before constructing any segmental retaining wall, the on-site soils engineer must verify and document that soils meet characteristics specified in the soils report and wall design.  Soil types vary tremendously in their response to water and effects on retaining walls.  Minimum infill soils need to meet requirements outlined in Section 1 Part 2.3 in the Allan Block Spec Book.  (ref. BP, Chapter 2.5)

Allan Block is working to achieve our industry initiative of Zero Wall Failures. With our Best Practices Manual and experience in the industry we are trying to expand the knowledge base for the design of segmental retaining walls (SRW's) by communicating and educating the professionals in the industry.  To see the full Best Practices Manual, visit allanblock.com to download today and keep an eye out for more industry Best Practice recommendations here.