How to attach and terminate geomembranes on a concrete structure
Hermann Ng, Director of Technical & Marketing APAC
HDPE and LLDPE geomembranes are commonly utilized as barriers and covers in various containment facilities, including solid waste landfills, liquid containment areas, mining ponds, agriculture, and aquaculture ponds.
The connection of geomembranes to concrete walls and ancillary structures, such as pipe penetrations or outlet structures under hydraulic pressure, plays a crucial role in ensuring proper sealing and preventing leakage. It is essential during installation to securely fasten the geomembranes in place and prevent them from sliding down. A conventional method for connecting geomembrane panels to concrete structures involves using a mechanical batten strip.
R. Thiel & G. DeJarnett reported potential issues encountered with connections using stainless steel batten attachments. Engineers and installers must pay attention to these concerns, particularly regarding the leak resistance of geomembrane penetrations and attachments to concrete structures. Some of the issues requiring attention include:
• Anchor bolt nuts becoming loose over time, leading to leakage past bolt holes.
• Gaskets leaking underneath battens.
• Compatibility and degradation of gaskets.
• Stress concentration at the base of the batten.
An alternative option for attaching HDPE geomembranes to concrete structures is the use of concrete embedment strips, such as "Polylock." Polylock is a sturdy and durable HDPE profile that can be easily installed by casting it in place or inserting it horizontally into wet concrete. Upon completion of the concrete preparation, the welding surface of Polylock remains exposed. These strips provide a high-strength mechanical anchor to secure the geomembrane to the concrete.
Polylock can be fabricated in various forms and placed in different orientations. When correctly installed and used in conjunction with a geomembrane, it offers excellent leak resistance. The anchor fingers of Polylock provide significant mechanical strength, resisting high pull-out forces when embedded in concrete and welded to the geomembrane.
A series of studies were conducted to evaluate the performance of the Polylock concrete attachment. Laboratory tests involved directly pulling out the Polylock profile in a direction perpendicular to the finished concrete surface. These tests demonstrated that the resistance to pull-out from concrete is much greater than the loading applied by any geomembrane welded to the Polylock surface during service. Testing also revealed that the pull-out resistance, under typical service loading conditions (shear), is generally two to three times higher than that of the geomembrane.
In general, Polylock is a more cost-effective option for attaching geomembranes to concrete structures, as it establishes a leak-resistant connection and ensures a completely watertight installed geomembrane liner system. It can be used on concrete pipes, manholes, sumps, and columns where geomembranes need to be penetrated, and where a sealed connection between the concrete structure and geomembrane liner is crucial. Some advantages of using Polylock include:
• Easy installation, especially in curved areas, and compatibility with various designs.
• Reduced liner runout.
• High strength.
• Robustness and durability.
• Excellent leakage barrier.