Soil- Geomembrane interfaces performance under monotonic temperature cycles: implications for infrastructure durability

• Soil-geomembrane interfacial behavior under monotonic temperature cycles studied. • Interface's resistance and friction angle reduce with ascending cycles. • Shear strength and friction angle under 5–20 °C cycles mirror 20 °C conditions. • Geomembrane micro-degradation lowers friction angle and shear under 50–20 °C cycles. • Soil-geomembrane interface friction and shear stabilize after three cycles. The exposure of soil-geomembrane interfaces to environmental temperature variations poses potential failure risks in geomembrane-lined structures, such as landfill side walls and water reservoirs. Despite recent studies, the behavior of these interfaces under monotonic temperature cycles remains unclear. This study aims to address this gap by examining the mechanical response, including interfacial properties and shear strength, of a soil-geomembrane interface subjected to stable (20 °C), low (5–20 °C), and high (50–20 °C) temperature cycles under various stress conditions for long-term performance. A series of interface direct shear tests were conducted on sand and high-density polyethylene (HDPE) geomembrane samples across four consecutive temperature cycles. Results indicated a reduction in shear strength at stable temperature cycles, ranging from 14.51 % after the first cycle to 18.57 % after the fourth cycle under 100 kPa normal stress, due to changes in the contact zone and failure mechanisms like sliding and plowing. Conversely, low-temperature cycles had minimal impact on shear strength, as the geomembrane's mechanical properties remained stable. The most significant reductions in shear strength, ranging from 21.10 % (after the first cycle) to 27.19 % (after the fourth cycle), were observed at higher temperature cycles, highlighting that elevated temperature cycles substantially compromise the shear strength of the soil-geomembrane interface due to the micro-degradation of geomembrane. This study highlights the necessity of considering temperature cycling in the design of geomembrane-lined infrastructure. It also recommends employing a geomembrane with high thermal resistance, typically associated with higher thickness, to ensure the infrastructure's durability and long-term performance.