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.

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.

Best Practices for Zero Retaining Wall Failures - Wall Rock Guidelines

Construction of Allan Block retaining walls should always include wall rock within the block cores and behind the block, which is typically 12 in. (30 cm) in depth. Section 1 Part 2.2 in the Allan Block Spec Book covers what type of rock is acceptable.  The height of the wall will determine the amount of wall rock needed behind the block and for walls with curves and corners, additional depth of wall rock should be specified to promote greater stability in these areas. At the top of the wall, above the wall rock it is also common to place a horizontal layer of landscape fabric to protect the wall rock from being infiltrated by the topsoil placed to finish the wall.

(ref. BP, Chapter 2.4)

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.

Best Practices for Zero Retaining Wall Failures - Allowable Infill Soils

The best soil to use behind your segmental retaining wall is wall rock or select/structural fill with less than 10% fines, to the limits of the geogrid lengths.  Sometimes on-site soils are acceptable to use as infill, be sure to check with the geotechnical engineer.  Heavy clays or organic soils, and poorly graded sands or expansive clays should not be used in wall construction.  Fine grained cohesive soils can be used, but additional backfilling, compaction and water management efforts are required.  For more information on infill soil, consult Section 1 Part 2.3 in the Allan Block Spec Book.  (ref. BP, Chapter 2.3)

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.

Best Practices for Zero Retaining Wall Failures - Allowable Foundation Soils

The soil below any segmental retaining wall will have a significant effect on the wall’s stability.  Foundation soils should be inspected by the on-site soils engineer to ensure they meet or exceed design soil parameters.  A geotechnical report should include parameters and recommendations for sub-soils.  If poor soils are encountered during construction, consult with the owner and geotech for removal and replacement recommendations.  For more information on soil preparation consult section 3.1 Foundation Soils in the AllanBlock Spec Book.  (ref. BP, Chapter 2.2)

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.

Best Practices for Zero Retaining Wall Failures - Inspection of Materials

In any construction practice it is crucial that the contractor inspect all materials upon delivery to the site to assure proper material has been received. When constructing a segmental retaining wall like Allan Block, it is the contractor’s responsibility to protect all materials from damage or contamination prior to use within the wall.  Always make sure that there has been no substitutions in geogrid or blocks.  Any changes in specified materials should be evaluated and approved by the retaining wall designer and may require redesign. (ref. BP, Chapter 2.1)

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.

Best Practices for Zero Retaining Wall Failures - Wall Embedment with a Slope Below

In cases where there is a slope below an Allan Block wall or a “toe slope”, it may be necessary to bury more block than usual.  Local ordinances commonly reference to bury enough blocks to have a 5 - 7 ft (1.5 - 2.1 m) level bench in front of the wall.  The 1 in (2.5 cm) of depth per 1.0 ft (30 cm) of wall height rule is used beyond that point. (ref. BP, Chapter 9.1) 

Allan Block is working to achieve a path towards an industry wide 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.

Best Practices for Zero Retaining Wall Failures - Wall Embedment

Allan Block retaining walls (and all segmental retaining walls) should include burial to prevent undermining due to erosion over time, but how much should you bury? Best Practices recommends 1 in (2.5 cm) of block per 1 ft (30 cm) of wall height, with a minimum of 6 in (15 cm). (Reference: Best Practice chapter 2.6) In cases where there is a slope above or below the wall, this recommendation will change. In these cases, feel free to call our engineering team at Allan Block or review other sections of Best Practice – for instance Chapter 9 section 9.1, embedment for slopes below the wall. (ref. BP, Chapter 2.6)

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.