Bituminous geomembranes (BGMs) are widely used in various geosynthetic applications due to their durability and flexibility. However, their performance can be significantly affected by exposure to heat and sunlight. Understanding these impacts is crucial for engineers and installers to ensure long-term functionality and avoid potential failures.
Key Findings from the Case Study
A case study from a co-disposal tailings storage facility in the Dominican Republic provides valuable insights into the performance challenges of BGMs under extreme conditions. Here are the main points:
1. Temperature Effects on Weld Strength
Issue: The case study highlighted that prolonged exposure to high temperatures can drastically reduce the weld strength of BGMs.
Findings: During the inspection, seams were observed to have poor tensile strength and could be pulled apart by hand. On-site testing revealed that exposure to elevated temperatures (up to 86.2°C) caused a significant reduction in seam strength. At 70°C, seam strength dropped to 3.9 kN/m from an initial 20 kN/m, demonstrating a severe decline.
2. Loss in Friction Performance
Issue: Heat exposure can also affect the friction performance of BGMs, particularly on slopes.
Findings: The friction angle between the BGM and underlying materials was compromised, leading to "necking" or stretching in areas where the slopes were too steep, even under its self-weight. This reduced friction increased the risk of slippage and compromised the structural integrity of the liner system. 3. Shear Strength Degradation
Issue: Even at realistic, ambient temperatures, BGMs can experience a loss in shear strength.
Findings: The case study recorded ambient temperatures of 37°C, leading to surface temperatures of BGMs reaching as high as 86.2°C. This resulted in delamination, surface deformation, and dripping bitumen, indicating that the material's shear strength was compromised.
Real-World Implications for Engineers
1. Surface Temperatures:
With ambient temperatures of 37°C, the BGM surface can reach up to 86.2°C. This near-softening point temperature of bitumen can cause significant material degradation. 2. Risk of Failure:
Engineers must consider the potential for reduced material performance due to heat exposure when designing and installing BGMs. Without proper precautions, there is a heightened risk of failure post-installation, particularly in hot climates.
Recommendations for Best Practices
1. Consult Experts:
Engage with geosynthetics experts who understand the limitations of materials under various environmental conditions. GeoKonect offers a platform to connect with such experts, ensuring that all potential risks are addressed during the design phase. 2. Site-Specific Testing:
Where possible, conduct site-specific testing to determine the real-world performance of BGMs under expected environmental conditions. This can help identify potential issues before they arise. 3. Material Selection and Innovation:
Consider alternative materials or innovative solutions that offer better performance under high temperatures. Suppliers are continually developing new products, and staying informed about these innovations is crucial.
Mitigating Risks: Lessons Learned
Based on the case study, several measures could have potentially avoided the issues observed:
Reducing Slope Angles: Implementing gentler slopes could have reduced the tensile stress on the geomembrane, minimising the risk of failure due to necking and seam separation.
Covering with Geotextile: While more expensive, using a protective geotextile or soil cover could shield the BGM from direct sunlight, reducing surface temperatures and preventing degradation. This additional layer would provide further protection against UV radiation and heat, preserving the material's integrity.
Adding a white coating: or embedding white within the BGM formula would have similar impacts that white coating induces with HDPE geomembranes, in that it reduces surface temperature by up to 50% in some cases, leading to slower aging but also maintaining mechanical values and laboratory performance indicators.
The Role of GeoKonect
At GeoKonect, we are committed to uncovering and sharing valuable insights about material performance to promote innovation and development in the geosynthetics industry. Our goal is to provide unbiased information that helps engineers make informed decisions, ultimately leading to safer and more effective projects.
By understanding the limitations of BGMs and taking proactive steps to address potential issues, we can improve the reliability and longevity of geosynthetic applications in even the most challenging environments.
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