Durability of three PVC-P geomembranes during two years of accelerated ageing laboratory tests

Overview & Synopsis

PVC-P geomembranes have demonstrated their performance in sealing shallow and medium-depth tunnels. In the case of very deep tunnels, there are additional issues, such as the higher temperature than at the surface. In the case of the future Lyon-Turin tunnel, depths can exceed 2000 meters, which can lead, due to the geothermal gradient, to temperatures exceeding 60°C. In these extreme conditions, the durability of PVC-P geomembranes remains to be demonstrated. Test specimens of three 3 mm thick PVC-P geomembranes, produced by 3 different producers, were placed for 2 years in 5 baths: 3 baths containing water at temperatures of 23°C, 45°C, and 70°C and 1 bath containing a sulfuric acid solution at 45°C and finally a last bath containing a calcium hydroxide solution at 45°C. At different immersion times in these baths (8, 12 and 24 months), test specimens were removed and mechanical tests (traction and static puncturing test) were carried out. Measurements of plasticizer contents were also carried out. The results show that the mechanical properties of the three tested geomembranes remained stable over time, as did the plasticizer dosage measurements.