Institute for Rural Engineering, NARO

Durability of the waterproof sheet confirmed after 50 years

- Verified by exposure test in practical environment -

The Institute for Rural Engineering, NARO (NIRE) has clarified the durability of the waterproof sheet used in agricultural reservoirs after 50 years of exposure in an environment where it is practically used. It has been verified that the durability of the waterproof sheet holds about 80% of the initial value if placed in water. This data can be used for maintenance and management of various agricultural irrigation facilities.


Waterproof sheet is used in the agricultural facilities such as waterways, reservoirs etc. for storage and distribution of water for agriculture. The waterproof sheet has a role to retain water (water tightness). However, sufficient data was not organized for the durability of the water impermeable sheet in the case of long-term exposure under a practical environment.

Therefore, the Institute for Rural Engineering, NARO(NIRE) has started a demonstration test in 1967 for the first time in Japan using a synthetic rubber type waterproof sheet used mainly in European countries and the United States as a water-blocking material for agricultural reservoirs. In 2017, after 50 years of installation, the tensile strength, elongation at rupture, tear strength etc. of the waterproof sheet on the bottom of the reservoir were analyzed. As a result, it was revealed that various physical properties of the waterproof sheet placed under water retained to about 80% of the initial value even if 50 years have passed after installation.

The waterproof sheet is used not only in agricultural reservoirs but also in waste disposal sites. The data obtained can be used as a reference in designing a durable waterproof sheet which can be used all over the country, maintenance of the facility, and in determining the expected time for renovation of the facility.

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Reference information

Fig. 1. Utilization of the waterproof sheet in agricultural irrigation facilities

Fig. 2: Appearance of the waterproof sheet from installation to the present

Table 1: Results of various tests on waterproof sheet after 50 years

The tensile strength and elongation at rupture can be obtained at the same time by tensile test. The data during the ※ test was deleted and average value is calculated, since the load greatly decreased at the initial stage of the displacement in the tensile test and there is a possibility of an abnormality such as a crack in the sheet.

Fig. 3: Test results