How do you design and install geosynthetic clay liners for landfill applications?

2 Design considerations

When designing GCLs for landfill applications, there are several factors that need to be taken into account in order to ensure the performance and durability of the liner. The type and quality of the clay material should have a low hydraulic conductivity, a high swell index, and be compatible with the leachate chemistry. The geotextile or geomembrane material should possess a high tensile strength, a high puncture resistance, and an effective interface friction with the clay and subgrade. The thickness and mass per unit area of the GCL should be sufficient to provide adequate hydraulic and mechanical properties, while also accounting for potential losses due to manufacturing, handling, or installation. Additionally, the slope and shape of the landfill should be compatible with the GCL installation and anchoring methods, so as to avoid excessive stress or deformation of the liner. Finally, it is important to assess the climatic and environmental conditions in order to determine how temperature, moisture, wind, and vegetation may affect the GCL's performance and durability.

3 Installation methods

When installing GCLs for landfill applications, there are two main methods to choose from: panel installation and roll installation. The choice of method depends on the site conditions, the availability of equipment, and the contractor's preference. For panel installation, pre-cut panels of GCL are laid on the prepared subgrade and secured with pins, staples, or sandbags. The panels should be overlapped by at least 300 mm and covered with a protective layer of soil or another geosynthetic material, which should be compacted to ensure good contact and seal. For roll installation, GCL rolls are unrolled on the prepared subgrade and secured with pins, staples, or sandbags. These rolls should also be overlapped by at least 300 mm and covered with a protective layer of soil or another geosynthetic material that should be compacted to ensure good contact and seal.

4 Quality control

Quality control is essential to guarantee the successful installation and performance of GCLs for landfill applications. This includes inspecting the GCL materials before delivery and during storage to check for defects, damage, or contamination. Additionally, the subgrade should be inspected before installation to make sure it is smooth, level, and free of sharp objects or debris. The installation process should also be inspected to verify that the overlaps, seams, and anchors are correctly placed and secured, and that the GCL is not damaged or displaced by equipment or personnel. After installation, the protective layer should be inspected to ensure that it is evenly distributed and compacted, and does not damage or expose the GCL. Finally, tests should be conducted after installation to measure the hydraulic conductivity, the interface friction, and the peel strength of the liner.

5 Maintenance and monitoring

Maintenance and monitoring are essential for the long-term performance and durability of GCLs for landfill applications. This includes periodically inspecting the surface of the landfill for signs of settlement, erosion, cracking, or leakage. Additionally, it is important to inspect the leachate collection and gas extraction systems to ensure they are functioning properly and not damaging or compromising the GCL. Furthermore, testing the leachate and gas quality and quantity can help assess the effectiveness and integrity of the GCL as a barrier. Lastly, any damage or defects in the GCL or protective layer must be repaired using appropriate materials and methods.