When designing containment systems for mining, engineers often begin with GRI-GM13 — the long-standing benchmark for HDPE geomembranes. But as Warren Hornsey, Scheirs, Will Gates, and Malek Bouazza demonstrated in their landmark paper “Impacts of Mining Solutions/Liquors on Geosynthetics”, the realities of chemical exposure in mining environments stretch well beyond what GM13 was ever intended to cover.

Their research compared the performance of geomembranes and other geosynthetics when immersed in various acidic, alkaline, and metal-laden liquors typical of heap leach and tailings facilities. The findings remain some of the clearest evidence that site-specific conditions directly determine polymer performance and lifetime.

Key findings from the research

1. Mining solutions are far more aggressive than MSW leachates. Liquors from gold, copper, and nickel operations routinely reach pH values below 2, with sulphate concentrations above 20,000 mg/L, and temperatures nearing 70 °C. Under these conditions, oxidation and stress crack initiation accelerate dramatically — particularly at welded seams and wrinkles under sustained load.
2. Standard stabilisers can fail in strong acids. The paper identified that HALS (hindered amine light stabilisers), widely used in polyolefins, lose effectiveness in low-pH environments. Once deactivated, antioxidants are consumed rapidly, leading to chain scission and early embrittlement.
3. Organic solvents can swell and weaken HDPE. In solvent extraction circuits where kerosene or other organics are present, HDPE can experience swelling and localised softening — creating wrinkles and stress zones that promote cracking.
4. Brines and high-pH residues degrade materials differently. Highly alkaline solutions, such as Bayer liquors, attack polymers and even the mineral components of GCLs. The paper emphasised that oxidative ageing pathways differ completely between acidic and basic chemistries.
5. MSW test data doesn’t represent mining exposure. Immersion studies revealed that antioxidant depletion in MSW leachate can be two to four times faster than in acidic solutions — proof that there is no universal ageing model. Longevity must be predicted using chemistry-specific testing.

The real takeaway: formulation must follow exposure

The core message from Hornsey et al. is not simply that geomembranes degrade — it’s that the mechanism and rate of degradation depend on the environment. Two sites may specify the same GM13 liner and achieve entirely different outcomes depending on:

• pH range (acidic tailings vs alkaline residues)
• temperature and heat cycles
• contact with organic solvents or process reagents
• metal content and oxidation potential of the liquor
• stress state and restraint conditions

This means that polymer formulation and stabiliser design must be tailored to the site, not the specification. Standard OIT or SCR values alone do not describe how a geomembrane will perform when immersed in strong acid or alkali for 20 years.

Why it changes how we specify

For engineers, this shifts the focus from compliance to context. Instead of asking whether a liner meets GM13, we must ask:

“Was it designed and validated for the chemical and thermal conditions of my site?”

Immersion testing, high-temperature OIT retention studies, and stabiliser compatibility with site chemistry are now essential design inputs — not optional research.

How the industry is responding

Manufacturers have begun to close the gap between generic standards and field performance. Atarfil’s EVO development program, for example, was born directly from these findings — testing HDPE geomembranes in low-pH acids, alkaline brines, and elevated temperatures to understand how antioxidant systems respond to real mining conditions.

The goal is not to redefine GM13, but to extend its relevance — using chemistry-specific immersion testing and stabiliser engineering so that design life predictions reflect the environments in which geomembranes actually operate.

Looking ahead

As the industry pushes for longer design lives and higher environmental assurance, “fit-for-exposure” will replace “fit-for-spec” as the defining measure of liner quality.

Hornsey et al.’s work reminds us that the durability of a containment system is determined not by the specification sheet — but by how well the material chemistry aligns with the chemistry of the site.

References

Hornsey, W.P., Scheirs, J., Gates, W.P., Bouazza, A. (2010). Impacts of Mining Solutions/Liquors on Geosynthetics. Geotextiles and Geomembranes 28: 191–198.