Non-aqueous-phase-liquid breakthrough during evaporative drying of clay barriers

Area of Science:

• Geotechnical Engineering
• Environmental Science
• Contaminant Hydrogeology

Background:

• Clay liners are crucial barriers in waste containment systems.
• Drying of clay liners can compromise their integrity and lead to contaminant leakage.
• Understanding non-aqueous-phase-liquid (NAPL) behavior in drying clays is vital for environmental protection.

Purpose of the Study:

• To model the penetration and breakthrough of NAPL in a drying clay liner.
• To investigate the relationship between clay drying rates, structural damage, and NAPL penetration.
• To develop a conceptual model for NAPL breakthrough in clay liners.

Main Methods:

• Monitoring water content of clay samples during ambient evaporation.
• Using clay drying rate as a key parameter for NAPL breakthrough analysis.
• Observing structural damages (cracks, suction) on clay boundaries.

Main Results:

• Clay drying rates influence structural damage formation and NAPL penetration.
• Capillary effects at NAPL-clay and clay-air boundaries are significant.
• NAPL breakthrough is associated with cracks initiated at the upper soil surface.

Conclusions:

• Drying-induced structural changes in clay liners significantly impact NAPL migration.
• A conceptual model linking drying, cracking, and NAPL breakthrough is proposed.
• Cracks forming on the upper soil surface are the likely pathways for NAPL breakthrough.