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

Guillaume Stoltz, Julien Aubriet, Gisèle Bambara, Laurent Sauger, David Chamoley, Sébastien Bouteille

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## To cite this version:

Guillaume Stoltz, Julien Aubriet, Gisèle Bambara, Laurent Sauger, David Chamoley, et al., Durability of three PVC-P geomembranes during two years of accelerated ageing laboratory tests. EU-ROGEO 8 - 8th European Conference on Geosynthetics, Sep 2025, LILLE, France. pp.01010, 10.1051/e3sconf/202564401010. hal-05461957

HAL Id: hal-05461957

https://hal.science/hal-05461957v1

Submitted on 16 Jan 2026

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

*Guillaume Stoltz¹*, *Julien Aubriet¹*, *Gisèle Bambara¹*, *Laurent Sauger²*, *David Chamoley³*, and *Sébastien Bouteille³*

¹INRAE, Aix Marseille Univ, RECOVER, Aix-en-Provence, France

²CEREMA, Lyon, France

³CETU, Lyon, France

**Abstract.** 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.

## 1 Introduction

Plasticized polyvinyl chloride (PVC-P) geomembranes are commonly used to ensure the waterproofing of tunnels, especially at medium and large depths, due to their flexibility and adaptability to complex structures [1].

Whether in tunnels or for other applications, the long-term durability of PVC geomembranes is a major concern. Indeed, this long-term durability determines the service life of the structures in which they are installed, especially if these geomembranes are very difficult to access for replacement, which is the case for tunnels at medium and large depths [1].

Depending on the structure in which they are installed, in service conditions, many factors and actions can affect the integrity and therefore the durability of geomembranes, such as weathering factors (UV radiation, extreme positive and negative temperatures involving frost, etc.), the media and the chemical species in contact with the geomembrane (aqueous, basic, acidic media, aerobic conditions, etc.), mechanical actions (falling stones, ice creeping, impacts by floating debris and boats, wind and waves, fauna and flora, vandalism, etc.) [2].

<footnote>* Corresponding author: guillaume.stoltz@inrae.fr</footnote>
In tunnels, geomembranes are not exposed to UV radiation or mechanical actions such as impact such as those mentioned above. The main ageing process that can lead to a degradation of the physical, mechanical and hydraulic properties of PVC-P geomembranes is the loss of plasticizers by diffusion processes. This mechanism of loss of plasticizers by diffusion has been studied by many authors in the case of PVC-P geomembranes used in non-exposed to UV conditions in basins or reservoirs, whether by covering with a protective granular layer or due to the position of the geomembrane under the water level [3]. Benneton et al. [4] has directly evaluated the loss of plasticizer of different PVC-P geomembranes from laboratory immersion tests for 10 years. It has been shown that, after 10 years of immersion, the loss of plasticizer was relatively limited (from 3 to 13% depending on the geomembrane studied) but the immersion tests were carried out in water of 15 to 20° C. To assess the loss of the geomembrane properties after accelerated ageing tests in laboratory, the tensile strength of the geomembrane after ageing is generally compared with the tensile strength of the virgin geomembrane. This method of assessing durability seems unsuitable for geomembranes whose function is the barrier function, i.e. "the use of a geosynthetic to prevent or limit the migration of fluids" (EN ISO 10318-1, [5]). However, in real conditions, geomembranes are confronted with mechanical stresses or deformations that can compromise their integrity, and therefore lead to a rupture of the barrier function, if they do not resist these actions. Comparing one or more mechanical properties of a geomembrane before and after ageing has thus become common practice [6]. Nowadays, there are now several standardized tests that allow accelerated ageing tests to be carried out in the laboratory for geomembranes: oxidation tests following EN 14575 [7], UV weathering tests following EN 1297 [8], water immersion tests following EN 14415 [9], chemical tests following EN 1847 [10], and microbiological tests following EN 12225 [11]. However, none of these different standardized tests satisfactorily reproduce the conditions of great depths tunnels. In this type of application, depending on the depth of the tunnel, the geothermal gradient can lead to significantly high temperatures, with basic or acidic conditions depending on the chemical nature of the rock. Luciani et al. [12] developed long-term immersion tests (ranging from 180 to 270 days) and at temperatures ranging from 45 to 75°C. However, although the geomembrane was in contact with a concrete sample, real acidic and basic conditions were not applied.

The present study evaluates by long-term laboratory ageing tests the durability of three thick (3 mm-thick) PVC-P geomembranes, specifically designed for very deep tunnels, such as the one currently being built between Lyon (France) and Turin (Italy). Samples of these three geomembranes were immersed for 24 months in water baths at different temperatures (23°C, 45°C and 70°C) and in an acidic water bath (at a temperature of 45°C) and finally in a basic water bath (at a temperature of 45°C). At different ageing times (8, 12, 20 and finally 24 months) mechanical tests (unidirectional traction and static punching) and plasticizer dosage tests were carried out.

# 2 Materials and Methods

## 2.1 Ageing laboratory tests

### 2.1.1 Temperature controlled tanks

The accelerated ageing tests were carried out in cylindrical stainless steel cells, with an internal diameter of 0.5 m and a height of 1.2 m. These cells are watertight and equipped with a heating resistor to regulate the temperature of the water inside with an accuracy of 2°C. In
addition, each cell is equipped with a pump to continuously circulate the fluid from the bottom to the top of the cell.

### 2.1.2 Ageing media

Three types of aqueous media were used to carry out the ageing tests:

- Demineralized neutral water,

- Acidic water containing 0.5% sulfuric acid $H_2SO_4$,

- Basic water containing a saturated $Ca(OH)_2$ solution.

For each geomembrane, five ageing conditions were applied:

- Immersion of the specimens at 70°C in neutral water,

- Immersion of the specimens at 45°C in neutral water,

- Immersion of the specimens at 45°C in an acidic medium,

- Immersion of the specimens at 45°C in a basic medium,

- Immersion of the specimens at 23°C in neutral water.

### 2.1.3 Experimental procedure

The ageing tests began in early September 2022 and ended after 24 months, i.e. in September 2024. At different ageing periods, i.e. at 8, 12, 20 and 24 months, specimens of each tested geomembrane were removed from the baths and mechanical and plasticizer dosage tests were carried out. All specimens removed from immersion are dried in an oven at 60°C ± 2°C for 48 hours and cooled in a desiccator to limit their reabsorption of moisture. At each time when some geomembranes specimens were removed from the baths, the entire liquid (demineralized neutral water, acidic water and basic water) was completely renewed.

### 2.1.4 Mechanical tests

The unidirectional tensile tests were carried out according to EN 12311-2 [13] which has an identical procedure as the EN 17323 standard [14] in the case of homogeneous PVC geomembranes (no reinforcement). For such unidirectional tensile test, a video-extensometer was used for the elongation measurement and all the tests were conducted until the rupture of the specimen. To determine the initial mechanical properties, in order to reduce the anisotropy of the materials due to the constraints induced by their manufacture, the specimens are placed in an oven for 6 h ± 15 min at 80 °C then 60 minutes at 23 ± 2 °C and 50 ± 5% relative humidity. To display the results of unidirectional tensile test, the force at rupture was divided by the nominal thickness of the three geomembranes. Static puncture tests according to the French standard NF P 84-507 [15] were also carried out. The sampling diagram of the unidirectional tensile dumbbell specimens and the square specimens (0.1 m x 0.1 m) on the aged geomembrane disks is shown in Figure 1. This sampling scheme ensures that unidirectional tensile properties are tested in all directions, without selected a specific direction (machine direction or cross machine direction).
<figure><img src="image_3.png" /><figcaption>**Fig. 1.** Schematic diagram of the sampling plan for geomembrane specimens on aged discs.</figcaption></figure>

### 2.1.5 Plasticizer content tests

To assess the loss in plasticizer following the ageing time, the plasticizer content was measured following the standard EN ISO 6427 [16].

## 2.2 Tested geomembranes

Three geomembranes PVC-P non UV were tested in this study. Since these three geomembranes were specifically produced for the tunnel between Lyon (France) and Turin (Italy), which is a very deep tunnel (depths almost everywhere exceeding 2000 metres), these geomembranes have particular specifications and in particular they have a nominal thickness of 3 mm. Hence these three geomembranes have the same nominal thickness of 3 mm. The producers of these geomembranes are MAPEI, RENOLIT and SOPREMA but for confidentiality reasons, they will be called A, B and C in the rest of the article (the order of the letters is different from that of the producers listed above).

# 3 Results

## 3.1 Uniaxial tensile strength and static puncture resistance

The tensile strength results for geomembranes A, B and C are displayed in Figures 2, 3 and 4 respectively and the static puncturing strength results are displayed in Figures 5, 6 and 7 respectively. After 24 months of ageing, regardless of the ageing condition imposed on the geomembranes, the relative stability of the measured values is observed on the graphics. No trend could be demonstrated. It is thus concluded that the three tested geomembranes in PVC -P 3 mm are durable according to the imposed ageing protocol.
<figure><img src="image_4.png" /><figcaption>Fig. 2. Tensile strength results for geomembrane A.</figcaption></figure>

<figure><img src="image_5.png" /><figcaption>Fig. 3. Tensile strength results for geomembrane B.</figcaption></figure>
<figure><img src="image_6.png" /><figcaption>Fig. 4. Tensile strength results for geomembrane C.</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>Fig. 5. Static puncture resistance results for geomembrane A.</figcaption></figure>
<figure><img src="image_8.png" /><figcaption>Fig. 6. Static puncture resistance results for geomembrane B.</figcaption></figure>

<figure><img src="image_9.png" /><figcaption>Fig. 7. Static puncture resistance results for geomembrane C.</figcaption></figure>
## 3.2 Plasticizer content

The plasticizer content results for geomembranes A, B and C are shown in Figure 8. As could be observed for the mechanical tests, after 24 months of ageing, whatever the ageing condition imposed on the geomembranes, a relative stability of the measured values is observed on the graphic. No trend could be demonstrated. These plasticizer content results are therefore in line with the mechanical results and it can be concluded that the three tested PVC-P geomembranes are durable compared to the conditions imposed on them in the study.

<figure><img src="image_10.png" /><figcaption>Fig. 8. Plasticizer content results for geomembranes A, B and C.</figcaption></figure>
## 4 Conclusion

This study consisted in studying the durability of three PVC-P geomembranes through long-term immersion tests (24 months) in temperature-controlled cells. These three geomembranes with a nominal thickness of 3 mm were specifically produced for the deep tunnel between Lyon (France) and Turin (Italy). For the immersion tests, 5 ageing processes were applied: immersion of the specimens at 70°C in neutral water, immersion of the specimens at 45°C in neutral water, immersion of the specimens at 45°C in an acidic medium, immersion of the specimens at 45°C in a basic medium and finally immersion of the specimens at 23°C in neutral water. At different ageing times, i.e. 8, 12, 20 and 24 months. specimens of the 3 geomembranes tested were removed from the baths and mechanical tests (unidirectional traction and static puncturing tests) and tests to determine the plasticizer content were carried out. For all the tests carried out, and for the three tested geomembranes, the results demonstrated that the values were stable, i.e. no upward or downward trend could be detected after 24 months of ageing, under the applied testing conditions. This conclusion is only valid within the framework of the experiments carried out and for the 3 geomembranes tested. It cannot be generalized to all PVC-P geomembranes because the composition of such geomembranes plays a major role in their durability. To attest the durability of another geomembrane subjected to conditions equivalent to those described in this study, a similar program should be carried out.

## References

1. A. Luciani, D. Peila, Tunnel Waterproofing: Available Technologies and Evaluation Through Risk Analysis. Int. J. Civ. Eng. **17**, 45–59, (2019)
https://doi.org/10.1007/s40999-018-0328-6

2. D. Cazzuffi, D. Gioffrè, Durability of exposed PVC-P geomembranes used for rehabilitating the upstream face of dams, in: Geosynthetics: Leading the Way to a Resilient Planet. CRC Press, pp. 1671–1677 (2023)

3. M. Blanco, A.M. Noval, E. Aguiar, G. Stoltz, N. Touze, F. Farcas, J.P. Giroud, Long-term performance of PVC-P geomembrane installed in “Los Llanos de Mesa” reservoir, Proceeding of the Conférence Eurogeo 7th, Warsaw (2022)

4. J.P. Benneton, PVC-P Geomembranes behaviour in a ten-year water laboratory immersion test. 5th International Conference on geosynthetics: 1105-1108. Singapore (1994)

5. EN ISO 10318-1, Geosynthetics Part 1: Terms and definitions (2015)

6. R.M. Koerner, Design with geosynthetics. Xlibris Corporation (2012)

7. EN 14575, Geosynthetic barriers - Screening test method for determining the resistance to oxidation (2005)

8. EN 1297, Flexible sheets for waterproofing – Bitumen, plastic and rubber sheets for roof waterproofing – Method of artificial ageing by long term exposure to the combination of UV radiation, elevated temperature and water (2005)

9. EN 14415, Geosynthetic barriers - Test method for determining the resistance to leaching (2004)

10. EN 1847, Flexible sheets for waterproofing - Plastics and rubber sheets for roof waterproofing - Methods for exposure to liquid chemicals, including water (2010)

11. EN 12225, Geotextiles and geotextile-related products - Method for determining the microbiological resistance by a soil burial test (2020)
12. A. Luciani, C. Todaro, D. Martinelli, and D. Peila, Long-term Durability Assessment of PVC-P Waterproofing Geomembranes through Laboratory Tests. Tunneling and Underground Space Technol., Volume **103** (2020)
https://doi.org/10.1016/j.tust.2020.103499

13. EN 12311-2, In Flexible Sheets for Waterproofing - Determination of Tensile Properties - Part 2: Plastic and Rubber Sheets for Roof Waterproofing (2013)

14. EN 17323, Geosynthetics - Determination of tensile properties of Polymeric Geosynthetic Barriers (2020)

15. NF P 84-507 Essais des géomembranes - Détermination de la résistance au poinçonnement statique des géomembranes et des dispositifs d'étanchéité par géomembranes - Cas du poinçon cylindrique sans support (1996)

16. EN ISO 6427 Plastics — Determination of matter extractable by organic solvents (conventional methods) (2013)