Using Geogrid to Reinforce a Retaining Wall

If your project involves stabilizing slopes or retaining earth, you will need geogrid. Geogrid is a synthetic, flexible mesh designed for these purposes, available in various materials, strengths, and sizes. Made from woven polyester or high-tensile strength plastic, it comes in rolls and is available in both uniaxial and biaxial forms. Biaxial geogrid, most commonly used for retaining walls under 10 feet, can be rolled in both directions while maintaining its reinforcement properties, unlike uniaxial geogrid, which can only be rolled out in one direction.

How Does Geogrid Work?

Definition: A geogrid is a synthetic material used in civil engineering for soil stabilization and reinforcement. It is typically made from polymers such as polyethylene, polypropylene, or polyester. Geogrids have an open-grid design, which allows soil to interlock within their apertures, creating a composite material with enhanced strength and stability.

Applications

• Road Construction: Geogrids are used to reinforce subgrade soils, reducing the risk of deformation and rutting. They distribute loads more evenly, increasing the road’s lifespan and reducing maintenance costs.
• Retaining Walls: By stabilizing the backfill, geogrids provide additional strength to retaining walls, allowing for steeper slopes and reducing the need for extensive foundation work.
• Pavement Design: Geogrids help to prevent cracks and extend the durability of pavement by reinforcing the base layers and reducing the need for thick layers of aggregate.

Materials

Geogrids are manufactured using high-strength polymers like:

• Polypropylene: Lightweight and resistant to chemical degradation, often used in softer soils.
• Polyester: Known for high tensile strength and used in heavy-load applications.
• High-Density Polyethylene (HDPE): Offers excellent durability and flexibility, suitable for varied environments.

The choice of material depends on project requirements such as load-bearing needs, environmental conditions, and compatibility with the soil.

Mechanisms of Action

• Interlocking: The open-grid structure of geogrids allows soil particles to lock into the apertures. This interlocking effect increases the composite material’s load-bearing capacity.
• Load Distribution: Geogrids distribute loads over a wider area, reducing localized pressure on the soil and preventing deformation.
• Shear Resistance: They provide resistance against lateral shear forces, improving stability on slopes and in embankments.
• Erosion Control: Geogrids reduce soil movement, protecting against erosion in areas with water flow or heavy rainfall.

Geogrids are indispensable in modern civil engineering projects. They enhance the performance and longevity of infrastructure by stabilizing soils, preventing deformation, and reducing construction costs. Their versatility in various applications, combined with their adaptability to different soil types and load requirements, makes them a critical component in construction and geotechnical projects.

Installing Geogrid with AB Aztec or AB Europa Walls

Geogrid reinforcement is a critical component when constructing AB Aztec or AB Europa retaining walls. Proper installation enhances the wall’s stability, prevents soil erosion, and ensures long-term durability. This guide provides a detailed process for incorporating geogrid into these retaining wall systems

Step-by-Step Installation

• Foundation Preparation: Excavate and level the base trench for the retaining wall, ensuring it is compacted and stable. Lay the first course of blocks on a level bed of compacted crushed stone, checking alignment with a level.
• Placement of the Geogrid: Measure the required length of geogrid based on the wall height and the manufacturer’s specifications. Cut the geogrid to the appropriate size using a utility knife or scissors.
• Positioning the GeogridLay the geogrid on top of the backfilled soil directly behind the first course of wall blocks. The geogrid should extend into the backfill perpendicularly to the wall face. Ensure that the geogrid is placed with the correct side facing up, as indicated by the manufacturer.
• Securing the Geogrid: Place the next course of blocks on top of the geogrid, pulling the geogrid taut before securing it in place. Backfill with crushed stone or gravel to the level of the geogrid. Compact the fill to eliminate air gaps and create a solid reinforcement layer.
• Repetition: Continue the process for additional layers of the wall. Add geogrid at specified intervals, typically every two to three courses of blocks, based on wall height and load requirements.

Tips and Precautions

• Follow Manufacturer Guidelines: Always adhere to the geogrid manufacturer’s specifications for spacing, overlap, and orientation.
• Avoid Wrinkles: Ensure the geogrid is taut and flat to maximize its reinforcing capability.
• Edge Safety: Trim any protruding geogrid to prevent it from interfering with adjacent landscaping.
• Proper Backfill: Use well-graded gravel or crushed stone for optimal drainage and compaction.
• Weather Considerations: Avoid installation during extreme weather conditions to maintain soil and block stability.

Installing geogrid reinforcement with AB Aztec or AB Europa retaining walls requires precision and adherence to proper techniques. By following this structured guide, you can build a sturdy, long-lasting retaining wall system that effectively resists pressure and environmental stress.

Compacting and Backfilling

• Wall Rock Installation: Fill the block cores and 12 inches (300mm) behind the block with wall rock. Use approved on-site soils or infill to backfill behind the wall rock to the height of the block.
• Compacting: Compact in lifts of 8 inches (200mm) or less, starting on the blocks and moving parallel to the block towards the excavation area. Make at least two passes with a plate compactor. The compacted soil should be solid and stable. Clear excess material from the top surfaces of the blocks, ensuring they are clean and smooth.
• Continuing Construction: Install the next level of blocks and geogrid as per the plan, repeating the steps to the desired height. Finally, fill behind the blocks with organic soil or approved on-site soil to prevent water from running behind the blocks and to support plantings above the retaining wall.

Installing Geogrid with AB Fieldstone Walls

• Foundation and Geogrid Placement: After installing the foundation, roll out the geogrid from the center of the AB Fieldstone facing back to the excavated area. Stack the next set of blocks (facing/anchoring unit) so the vertical seams are offset by at least 3 inches (75mm) or ¼ the block length.
• Tensioning and Staking: Remove slack from the geogrid and stake it before installing wall rock and infill soil. Avoid running compaction equipment on the geogrid.

Creating Patterned Retaining Walls

• Design and Installation: Patterned walls offer a unique look, blending different block sizes to create a hand-laid stone appearance. You can use preset patterns or design your own. For curved or reinforced walls, use a two-procedure pattern.
• Craftsmanship and Detail: Creating a hand-laid wall look requires craftsmanship and attention to detail. Allow extra time, especially if it’s your first attempt. Use either the AB Europa or AB Collection for preset or irregular patterns, refer to the Pattern Chart for details. Ensure a level surface on the reinforced wall for irregular patterns to properly install the geogrid.

Biaxial Geogrid: Applications and Benefits

Biaxial geogrids are crucial for creating stable landscapes that resist erosion. They are composite or plastic lattice structures used to reinforce roads, retaining walls, and slopes. Providing stability in both latitudinal and longitudinal directions, biaxial geogrids are durable and made from punched or extruded polymers, preventing soil erosion effectively.

Geogrid Properties

Geogrids have several properties that make them useful for construction:

• Tensile Strength: Resistance to breaking under tension.
• Radial Stiffness: Load distribution in all directions.
• Confinement: Prevents granular material like soil from shifting.

By locking soil particles in place, geogrids create long-lasting, erosion-resistant soil structures, reducing maintenance needs.

Common Applications

Geogrids are widely used in:

• Road Construction: Increasing roadway lifespan by strengthening the subgrade and evenly distributing vehicle weight.
• Retaining Walls: Reinforcing soil behind walls to reduce pressure and prevent failure.
• Slope and Soil Stabilization: Allowing steeper slope construction by stabilizing layers of soil with geogrid.

Biaxial geogrids, with their ability to lock soils and add strength in multiple directions, are invaluable for construction projects. Ensure your projects stand the test of time by incorporating biaxial geogrid.