In recent years, toward the solution of worsening environmental problems, sustainable town development is also sought in the civil engineering field. Under such circumstances, the soft ground measures that used a lot of logs are expected from both sides of the disaster prevention and global warming mitigation. In order to expand the use of soil stabilization, we need to verify the unclear long-term stability of wood installed inside the ground, however there are not many studies about it. In this study, we examine the soundness interms of state of rotting of tree groynes installed underground for periods as long as 20years. We examine both visually as well as using the Pilodyn test, focus to the differences in the installation environment. Our results show that for the ground region of high water permeability where there is tide level fluctuation, it is clear that the installed wood in underground is suffered rot and insect damage. On the other hand, it is also seen that under similar conditions, the installed wood in underground is not suffered rot or insect damage in sections of permanently saturated soil capillary action, and also the soundness of the structures can be maintained over long periods of time.

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We conducted indoor tests to evaluate termite control in two different types of rubber ［non-vulcanized butyl rubber and ethylene propylene diene monomer （EPDM）］ with or without added anti-termite chemicals for termite-proofing the penetrations of plumbing in the foundations of wooden houses. In addition, we designed sample materials, which had a shape likely to be used in the actual site in the sleeve pipe method, for both supply and drainage piping. We examined the termite-proofing performance of each sample material by the field tests.
For the results of the indoor tests, boring by termite was observed in the non-vulcanized butyl rubber without added disodium octaborate tetrahydrate （DOT）. Furthermore, boring by the termite was inhibited by DOT added to the non-vulcanized butyl rubber and absolutely none were observed in the non-vulcanized butyl rubber with added 0.175% bifenthrin. In the field tests, no feeding damage or penetrations by termite were observed in the non-vulcanized butyl rubber, regardless of whether it contained DOT. In the indoor tests, EPDM packings showed similar tendency as that observed in non-vulcanized butyl rubber. However, for the supply and drainage piping of EPDM packing, feeding damage because of the termite was not observed in the field tests.
Because the leaching of DOT from the non-vulcanized butyl rubber and EPDM packing was slight in each test, it is recognized that these rubber materials maintain an effectual termite control function for a long period. It is confirmed that these rubber materials were probably enough to use for termite control in plumbing penetrations in the foundation of wooden houses.

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