3.1. Geogrid Reinforcement Benefits

Geogrid has been used to reinforce road sections. The inclusion of geogrid in subgrades changes the performance of the roadway in many ways (6).

Geogrids are materials made of high tensile strength polymers that are used to reinforce the soil beneath roadways. Their inclusion helps improve the overall performance of the roadway by providing support to the soil, allowing for better distribution of loads and increased stability.

Imagine trying to hold up a large piece of cardboard with your hands. If you just apply pressure to the center, it might bend or collapse. However, if you spread out some string or mesh underneath it, you can support the entire structure more evenly. The geogrid acts like that mesh, helping the roadway endure better under pressure.

Tensile reinforcement, confinement, lateral spreading reduction, separation, construction uniformity and reduction in strain have been identified as primary reinforcement mechanisms.

The primary benefits of using geogrids include several mechanisms:

• Tensile Reinforcement: Geogrids help resist the tension that occurs when loads are applied, keeping the soil stable.
• Confinement: They confine the soil particles, preventing them from shifting and losing their structural integrity.
• Lateral Spreading Reduction: Geogrids reduce the lateral movement of soil, which can occur under load. This helps maintain the correct shape and position of the roadway.
• Separation: Geogrids can separate different soil layers, preventing them from mixing.
• Construction Uniformity: They help distribute the load evenly during construction, enhancing the quality of the roadbed.
• Reduction in Strain: This helps to minimize deformation that might occur over time with traffic loads.

Think of a geogrid as the fabric in a strong backpack. Without the fabric, the backpack's contents would spill out when heavy loads are added. The fabric keeps everything organized, evenly supports the weight, and prevents the backpack from stretching or tearing.

Empirical design and post-construction evaluation have lumped the above described benefits into better pavement performance during the design life.

Studies and evaluations after construction have shown that using geogrids leads to improved pavement performance throughout its lifecycle. This means that roads reinforced with geogrids tend to last longer and require less maintenance than those without. The benefits noted earlier collectively contribute to this enhanced performance.

Consider a well-supported garden trellis that helps plants grow strong and healthy. The trellis provides support and keeps the plants from bending over under the weight of fruit or flowers. Similarly, geogrids support the road structure from below, helping it to withstand traffic loads and weather effects, leading to a healthier, more durable road.

Geogrid with reduced aggregate thickness option is designed for urban area and recommendations are follows; Excavate subgrade 9 in. (230 mm) and construct the subgrade with compacted aggregate No. 53 over a layer of geogrid, Type I. This geogrid reinforced coarse aggregate should provide stable working platform corresponding to 97 percent of CBR.

When using geogrids in urban areas, specific design recommendations suggest that the subgrade (the layer of soil or rock that supports the road) should be excavated to a depth of 9 inches. Then, a stable layer of compacted aggregate is placed on top of a geogrid. This setup not only supports the load but also meets a specific standard of robustness known as the California Bearing Ratio (CBR), indicating the strength of the subgrade materials.

Think of it like preparing a cake. You must layer your ingredients carefully to ensure it turns out just right. In creating a road, excavating and layering geogrid and aggregate is like getting the cake layers perfect—each layer needs to support the next for a firm, long-lasting cake that doesn’t collapse.

--