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Allan Block System

Commercial Installation Manual for Allan Block Retaining Walls
Check out all of the information we have on how to build a retaining wall and attend an AB Contractor Certification Training to learn the proper techniques to ensure top quality retaining walls are built.
   

Allan Block Retaining Wall Products and Collections
A Complete Family of Wall Products
The Allan Block Collections give you a choice of styles to meet your site and design requirements.
   

AB Collection - Retaining Wall
The AB Collection is our most popular retaining wall collection.
Whether you are building a simple raised garden or tackling a major hillside, the AB Collection will provide just what you need.
Chart showing multiple sizes, and shapes.
Photos of projects using our AB Collection.
   

AB Aztec - Retaining Wall
AB Aztec Collection brings ancient sophistication to modern retaining walls.
Whether you are building a simple raised garden or tackling a major hillside, the AB Collection will provide just what you need.
Chart showing multiple sizes, and shapes.
Photos of projects using our AB Aztec Collection.
   

AB Metropolitan - Retaining Wall
With minimalistic aesthetics and smooth clean lines, the AB Metropolitan line of blocks main focus is on functionality
This style offers a solution for a variety of wall applications, ranging from small residential to large-scale commercial projects.
Chart showing multiple sizes, and shapes.
Photos of projects using our AB Metropolitan Collection.
   

AB Europa - Retaining Wall
The AB Europa Collection offers the look and feel of weathered stone to the landscape.
The hand laid stone effect brings European old world charm and distinction to any retaining wall project.
Chart showing multiple sizes, and shapes.
Photos of projects using our AB Europa Collection.
   

AB Fieldstone - Retaining Wall
AB Fieldstone is our Green retaining wall product. This two-piece system has a facing unit and an anchoring unit.
Allan Block has opened the door to many benefits that are not only Green, but Natural and Friendly as well.
Chart showing multiple sizes, and shapes.
Photos of projects using our AB Fieldstone Collection.
   

What is a Retaining Wall
Gravity Wall or Geogrid Reinforced Wall?
Types of Retaining Walls
Understanding the dynamics of How Retaining Walls Work   Allan Block Video Logo
   

The Allan Block System - Engineered for Simplicity
Built-In Interlock
Built-In Setback
Built-In Drainage
Hollow-Core System
   

Gravity Retaining Walls
A retaining wall that relies solely on its own weight to stand up is called a gravity wall.
Setback and Sliding Wedge
Leverage and Total Unit Mass
Gravity Wall Maximum Wall Heights
   

Sample Gravity Wall Calculations
Analyze a gravity wall with the following site conditions:
   

Reinforced Soil Walls
When retaining wall heights exceed those listed in the gravity wall chart, geogrid can be added to provide a stable retaining wall condition
Geogrids are flexible, synthetic meshes which are manufactured specifically for slope stabilization and earth retention.
Positive Interlock
External and Internal Stability
   

Other Reinforcement Options
Masonry Reinforcement
Earth Anchors
No-Fines Concrete
Soil Nailing
   
Plan/Design

Retaining Wall Planning
Develop an accurate understanding of the jobsite before beginning any design, engineering, or construction on a project.
Site Geometry including Soils.
Water Management including Grading, Drainage, Surcharges, Slopes, and Setback.
Global Stability
   

Retaining Wall Design
Proper retaining wall design requires evaluation of the following:
Wall Location, Wall Height, Structural Requirements, and Total Structure.
Materials and Site Checklist Prior to Construction
Check Materials, Delivery Storage, Wall Rock, Backfill Soils, Foundation Preparation, and Geogrid Layout.
   
Build with AB, AB Aztec, AB Metropolitan, and AB Europa Collections

Gravity Retaining Wall Construction
Site Prep and Excavation
Install Base Material and Base Course
Install Wall Rock
Install Additional Courses
   

Stepping up the Base Course on a Slope
   

Reinforced Wall Construction
Site Prep and Excavation
Install Base Material and Base Course
Install Wall Rock and Backfill Material
Compaction, Install Geogrid, and Install Additional Courses
Installation Steps to Build a Proper Base Trench for AB Retaining Walls   Allan Block Video Logo
   

Modifying Blocks and Caps
Inside and Outside Corners
Cutting Caps for Corners and Curves
Altering Blocks
Construction Tips for Patterned Walls
   

Working with Geogrid
Retaining wall block can be used to construct walls that retain, or prevent the movement of the soil. The maximum height these walls can be built without the use of reinforcement is dependent on these primary conditions.
How Does Geogrid Work?   Allan Block Video Logo
   

No-Fines Concrete Backfill
Use of AB No-Fines Concrete Backfill has increased our ability to install reinforced retaining walls in locations where typical construction would not be possible because of property line constraints or limited excavation options.
No-Fines Engineering Properties
   

No-Fines Concrete Backfill
No-Fines Concrete Installation Steps
Additional Courses
Finishing Options
No-Fines Chart
   

Working with Soil
The soils used below and behind the wall are a critical part of the total wall structure.
A reinforced retaining wall is a structure containing three basic building materials - the block facing, the synthetic geogrid reinforcing materials, and the infill materials surrounding the geogrid layers
Soils and Soil Selection
Typical Friction Angle and Soil Unit Weights Chart
   

Retaining Wall Compaction
Proper placement and compaction of the infill soils are critical.
The most important step in getting proper compaction.
The consolidation zone runs from the back of the block back 3 ft (0.9 m) into the infill soil.
   

Water Management
The design and performance of most retaining walls are based on keeping the reinforced zone relatively dry.
Things to consider in our design:
Grading, Ground Water, and Concentrated Water Sources.
   
Build Patterned Walls with AB, AB Aztec and AB Europa Collections

Retaining Wall Patterns
All of the Allan Block Collections can be used to create a variety of pre-set and random patterned retaining walls.
Two and Three Course Patterns
Lite Patterns using the smaller blocks in the Collection.
   

Pattern Wall Construction
Excavate and Install Base Course
Install Geogrid
Install Course Pattern
Ending and Topping off Wall
   

Patterned Wall Construction Tips
Installing Reinforcement
Ending and Topping off the Retaining Wall
Curves and Corners
Stairs, Step-Ups and Tips for Patterned Walls
   
Building with AB Fieldstone

AB Fieldstone Gravity Wall Construction
Base Coursse and AB Fieldstone
Installing Wall Rock and Backfill Materials
Additional Courses for AB Fieldstone
Stepping up the Wall Base
   

AB Fieldstone Reinforced Wall Construction
Install Base Course for AB Fieldstone
Install Wall Rock and Backfill Materials
Compaction and Installation of Geogrid
Backfill & Compact with Additional Courses
   

Finishing an AB Fieldstone Wall with Caps
Filter Fabric Above Top Block / Below Cap
Capping Step-Downs
   

AB Fieldstone Construction Tips
Inside and Outside Curves with AB Fieldstone
AB Radius Chart for the Base Course of AB Fieldstone
Modifying Anchoring Units
   

AB Fieldstone Stepping Down
Creating a step down is similar to building an outside corner as it uses the same facing units that are manufactured with a textured side and has the same placement of the anchoring units.
When Stepping up the Wall Base is Needed
   

AB Fieldstone Stairs
Stairs can be designed with flowing curves or straight lines. Curved sidewalls create a softer, natural look. Straight sidewalls and corners o?er a crisp, traditional style. Building stairs requires careful planning and flexibility and will take extra time to design and build.
   

AB Fieldstone Parapets
How to Build a Parapet or Double Sided Wall
Using Dogbone for Interlocked Parapets
Standard Parapets, Wider Parapets and Curved Parapets
   
Construction Details with AB, AB Aztec, AB Metropolitan, and AB Europa Collections

Finishing Retaining Walls
Ending and Topping Retaining Walls
Building Step Downs
Building Turn-in Retaining Walls
   

Building Curves and Serpentine
Inside and Outside Curves
Building Tighter Curves
Working with Radii
AB Radius Chart for the Base Course
   

Building Corner
Inside and Outside Corners
Altering AB Corner Blocks for Different Setbacks
Installing Geogrid on Inside and Outside Corners
   

Proper Stair Construction for Retaining Walls
Stair Design
Stair Applications
Basic Stair Construction
Stair Tread Options
Ideas for Designing Stairways   Allan Block Video Logo
   

Building Terraces
It is often more aesthetically pleasing to replace one large retaining wall with two or more smaller terraced walls. Terraced walls can act as surcharges and may create global instability, therefore reinforcement may be necessary.
   

Building Water Applications
Retaining walls constructed in conditions where there is moving water (streams), standing water with wave action (lakes), or retention ponds are considered water applications.
Water applications must be evaluated and designed to fit the unique characteristics of the site. Consult with a local qualified engineer for design assistance.
   

Adding Fences, Railings and Gates
There are several options for installing fences and guide rails on top of an Allan Block retaining wall. The structure and wind loads of the materials used will determine the placement of the fence relative to the retaining wall and if additional reinforcement is required. Refer to the approved plans for construction details.
Sleeve-IT
   

Lighting for Retaining Walls
Lighting brings new possibilities to any landscape. Add a dramatic look with ground mounted lighting or illuminate stairways and pathways with recessed lighting. Allan Block walls with decorative lighting fixtures provide not only a distinctive design, but adds safety and security to the landscape.
   

Design Details for Allan Block Retaining Walls
Allan Block has a library of design details - cross section drawings to assist the design community in efficiently creating professional documents for our retaining walls and fence system.
Typical Details, Drainage Details, Fence Details, Water Applications Details, AB Fieldstrone Details, and Additional Details
   

Construction and Inspection Checklist
Review Wall Design Plans For:
Compliance of Site to Latest Site Plan
Review of Reported Soil Conditions with On-Site Soils Engineer
Review of Above Grade Water Management with Project Civil Engineer
   

Material Estimation Worksheet
Examples for Material Estimation including:
Geogrid
Drain Pipe
Infill Soils
   

Define Terms
Define Terms:
Base Material, Reinforced Zone, Consolidation Zone, Compaction Zone, Geogrid, Infill Soils, Drain Pipe, and Wall Rock.
   

Estimating Chart (Geogrid & No-Fines)
Surcharge Cases
Design Parameters
Geogrid
   
Specifications

Wall Specifications
Section 1 General
Section 2 Materials
Section 3 Wall Construction
   

Geogrid Specifications
Section 2 Part 1 General
Part 2 Materials
Part 3 Wall Construction
   

Leed Chart
What is LEED?
How Can Allan Block Products Help Your Project Achieve LEED Credits?
LEEDs Charts
   

Glossary
Glossary
Glossary of Terms
   
Charts and Tables

Standard Product Specifications Chart
Table 1.2 - Chart
   

Gravity Wall Heights Chart
Table 1.3 - Chart
   

Soils Chart for Retaining Walls
Table 2.1 - Chart
   

AB Setback Chart
Table 2.2 - Chart
   

Typical Friction Angle and Soil Unit Weights Chart
Table 3.1 - Chart
   

AB Radius Chart for the Base Course
Table 6.1 - Chart
   

Estimating Chart (Geogrid & No-Fines)
Surcharge Cases
Design Parameters
Geogrid
   

Leed Chart
What is LEED?
How Can Allan Block Products Help Your Project Achieve LEED Credits?
LEEDs Charts
   

Reinforced Soil Walls

Concept

When retaining wall heights exceed those listed in the gravity wall chart, geogrid can be added to provide a stable retaining wall condition. Layers of Geogrid inserted between the blocks and extending behind the retaining wall interlock with the surrounding soil to create a cohesive soil mass. This mass uses its own weight and internal shear strength to resist both the sliding and the overturning pressures from the soil being retained. The wall rock in the Allan Block cores provide a positive connection between the layers of geogrid and the Allan Block retaining wall, locking the two systems together. The reinforced soil mass becomes the structure and the Allan Block retaining wall becomes the facing. The specific location and embedment length of the grid layers depends upon the site conditions, wall heights and Long-Term Allowable Design Strength of the grid being used. See the approved plans for exact geogrid locations or consult with a local engineer.

Great Wall of China

The Great Wall of China, dating back some 2,200 years, was built as a double sided retaining wall. The soil between the two walls was a mixture of clay and gravel reinforced with Tamarisk branches. Allan Block retaining walls employ “old technology with new materials.”

Geogrids

Geogrids are flexible, synthetic meshes which are manufactured specifically for slope stabilization and earth retention. These “grids” are available in a variety of materials, sizes and strengths. They can be made of high tensile strength plastics or woven polyester yarns and are typically packaged at the factory in rolls. The grids are rated by Long-Term Allowable Design Strength (LTADS) with values ranging from 500 to 4,000 pounds per linear foot (7.3 kN/m to 58.4 kN/m).

For additional geogrid installation information, see the Reinforced Retaining Walls page or Designing Balance: Practical Guidelines.

Below is a listing of geogrid manufacturers. The geogrid has been tested with the Allan Block Retaining Wall systems for connection strength. Included is information and specifications on the each in Acrobat format (.pdf).

Geogrid Roll

Reference 1

Geogrid Installed on a Retaining Wall

Positive Interlock

Allan Block’s gravel filled hollow core provides a multi-point interlock with the grid. As retaining wall heights increase, our exclusive “Rock-Lock” connection, combined with the weight of the wall blocks, provides the best block-to-grid interlock of any system on the market. See the tech sheets on connection testing or the Seismic Testing Executive Summary for testing results on the “Rock-Lock” connection. Connection strength testing has been done with our grid manufacturers for results see the AB Spec Book or AB Engineering Manual.

Reference 1    Reference 2    Reference 3    Reference 13

Rock Lock Connection
Block to Grid

Analysis

External Stability

External stability exists when the entire wall system - the Allan Block facing units and the reinforced soil mass - act as a coherent structure to satisfy standard gravity wall analysis. Proper retaining wall design must satisfy all four of the following considerations.

Sliding

Sliding

Bearing

Bearing

Overturning

Overturning

Global

Global
Internal Stability

Internal stability is the ability of the reinforcement combined with the internal strength of the soil to hold the soil mass together and work as a single unit.



Grid Rupture on a Retaining Wall


Grid Rupture
Rupture that occurs when excessive forces exceed the ultimate tensile strength of the geogrid.
Increase grid strength or the number of grid layers.



Grid Pullout on a Retaining Wall


Pullout
Pullout results when grid layers are not embedded are not a sufficient distance beyond the failure plane.
Increase embedment length



Bulging Retaining Wall

Bulging
Pullout results when grid layers are not embedded a sufficient distance beyond the failure plane.
Increase number of grid layers.

Internal Compound


Internal Compound
Internal Compound instability occurs when a slip arc passes through retained soil, reinforced soil, and facing.
Increase length, strength, or decrease spacing of grid, use select infill material.

Reference 1    Reference 12    Reference 17

Design Considerations
  • Grid strength Select the right strength grid for the job. Choose LTADS grids from 500 lb/ft to 4000 lb/ft (7.3 kN/m to 58.4 kN/m).
  • Embedment length Grid length must extend far enough behind the wall to create a sufficient reinforced gravity mass. Typically a minimum of 60% of total wall height.
  • Number of layers Install enough layers to adequately increase the internal strength of the soil mass and handle all applied loads.
  • Spacing between layers Grid layers must be correctly spaced to distribute internal forces. Typically spaced on 16 in. (405 mm) centers.
  • Connection strength Block and geogrid must work together to resist internal forces.
AB Geogrid Retaining Wall Typical Section