March 22, 2019

Can Allan Block be Used in Water?

Written by: Ryan Miller


Rendering #1
Can Allan Block be used in water?  Absolutely!!  Many of the site challenges Allan Block products are used to solve include “water applications.”  What is a water application?  A true water application includes water being present all the time (such as a pond) or in some cases only periodically such as detention pond (water levels rise with rain events).  No matter the reason for the water application Allan Block can be used to solve your problem! 

Design and construction of a water application is virtually the same as a traditional Allan Block retaining wall project.  However, we do recommend the following when building a water application:
Detail #1
  • Removal of all clay and use of free draining aggregate known as wall rock within the wall system.
  • The four-inch drain pipe should be placed above the low water level.
  • Embankment protection fabric should be used behind and under the reinforced zone to protect fines from migrating into the mass.
  • Rip-rap should be used at the front of the wall to protect from erosion (specifically when the water is going to be moving).

*Check out Detail #1 and Rendering #1 for more information on recommendations.




For more information on building with Allan Block in water, check out our SRW WaterApplications Technical Newsletter or allanblock.com

January 3, 2019

Best Practices for Zero Retaining Wall Failures - Plantings with a Retaining Wall


In general, plantings in the reinforced zone are acceptable and may in fact enhance the reinforced soil mass provided:
  • Engineer should review with the owner the planting plans from the landscape architect to verify size of root balls and if any geogrid layers will be disrupted.
  • Language can be placed in the project specifications.
  • Augers should never be used within the reinforced grid zone.
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.

December 27, 2018

Best Practices for Zero Retaining Wall Failures - Slopes Above the Wall


Many retaining walls are designed with slopes above.  Slopes above a wall are okay, but there are limits to the steepness of slopes that must be considered.

In static designs, the maximum unreinforced slope above any wall cannot exceed the friction angle of the soil used to reconstruct the slope.

In seismic designs, the maximum unreinforced slope above any wall cannot exceed the friction angle of the soil used to reconstruct the slope minus the seismic inertial angle. The seismic inertial angle is determined by the soils engineer for that specific project site.

If the desired slope above exceeds either of the two limits above, the designer must analyze the slope above in a global stability program and provide slope reinforcement as required.

For any wall having a slope above greater than 3:1, and/or any slope with poor soils or walls with seismic requirements, it is recommended that the designer call for the slope to be reconstructed with stabilizing geogrid layers. These layers typically match the standard grid lengths in the wall along with their spacing.

The soil within the slope must also follow proper lift and compaction parameters within the geotechnical recommendations.  For more, see Chapter 6.0 Soils and Compaction.   (ref. BP, Chapter 12.3-6)

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.




December 20, 2018

Best Practices for Zero Retaining Wall Failures - Fences and Railings




Fences are very commonly found above retaining walls.  If a fence is going to be added to the wall during or after the wall’s construction several things need to be considered.

Impact structures or fence posts should be positioned a minimum of 3 ft (0.9 m) from the back of top course to allow a properly designed load for local overturning.

If fence posts must be placed within 3 ft (0.9 m) of the back of the wall facing, the designer must consider the localized top of wall overturning force into their design.

Common post footings are formed by using construction tubes placed at desired on-center locations during construction. If posts are placed after construction is complete, holes must be hand dug as using a power auger will cause severe damage to the geogrid layers.

If the post design calls for an engineered product to solve localized overturning forces, a product such as the Sleeve-IT System can be specified. Sleeve-IT is a Stratagrid product designed for use in segmental retaining walls to resist top of wall overturning forces from fences and railing. (ref. BP, Chapter 12.2)

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.