Click on the topics below to view more information on the best practices for Allan Block segmental retaining wall design for residental and commercial applications.
Design Guidelines Item: The term, "owner" refers to the property owner or their designated representative.
8.1 Tall Wall Considerations are to be employed with structures rising to a height of between 3 – 4.6 m, depending on the application and thediscretion of the wall design engineer.
A 3 m high wall structure with a slope or structure above would be considered as a tall wall, while the same wall height constructed with a level condition above the wall without any additional surcharge may not require consideration as a tall wall.
Figure 8-1: Variable Wall Rock Thickness
Several factors may change a typical design when structures reach these defined higher levels such as the depth of wall rock, increased design parameters, enhanced structural fill and global stability analysis requirements.
8.2 Wall rock depth behind the block and material used.
8.3 For tall walls the engineer should increase design parameters of compaction and wall rock usage.
8.4 As walls increase in height the active earth forces also increase in the lower portion of the wall. Therefore it is not uncommon in taller walls to increase the strength of the lower geogrid layers or decrease the grid spacing to accommodate the higher design forces.
8.5 The overall global stability of tall walls must be considered separately from the standard wall design to ensure the stability of the entire project site. For more information on global stability see Chapter 9.0 Global Stability - General and Chapter 10.0 Global Stability - Terraced.
8.6 Internal Compound Stability (ICS) calculations provide insight into potential global or overall stability issues. When more than 50% of the slip arcs originate at the back of the design envelope, as defined in Chapter 1, Section 1.7 b, a full global/overall stability analysis should be recommended to the owner by the owner’s geotechnical engineer.