Evaluation of the long term durability of water expansive
Masahiro OHTSUKA1, Toru KOBAYASHI2, Atsushi
1. Tokyo Electric Power Company; 2. Nippon Civic Consulting Engineers Co.,
Ltd; 3. Waseda University
Proceedings of the JSCE, No.707/VI-55, pp.101-110. June 2002.
Key words: Shield tunnel, segment lining, waterproofing design, water expansive
sealing material, durability, waterproofing material test
Water expansive sealing materials for waterproofing shield tunnels were developed
in the early 1980s. They had performed well for up to about 20 years, but there
was no assurance of long term durability, no method of testing durability,
and no criteria for evaluating sealing efficacy.
The research focused on the waterproofing function required from sealing materials
and set durability evaluation criteria. Eleven criteria were proposed for evaluating
the required durability of sealing materials, and an investigation into the
mechanisms of the waterproofing function of water expansive sealing materials
was carried out. A temperature accelerated durability test was proposed and
a method of setting the appropriate test temperature in this test was developed.
It was concluded from the results of tests carried out that the waterproofing
performance of rectangular water expansive seals based on natural rubber and
urethane materials commonly used for sealing could be maintained for at least
30 years. This research has equipped us with the technical know how for quantitative
incorporation of waterproofing materials into design with regard to durability.