Abstract
Fence work has been conducted to control the soil erosion and recover the vegetation, and numerous wood posts are installed as fence materials. To evaluate the service lives of the wood posts in the practical conditions, 44 executed sites were surveyed in Toyama Prefecture at III times. The survey was consisted of the visual inspection on-site and the mechanical testing of sampled pieces. The former was conducted by visual grading of 15 posts according to the FFPRI method shown in Table 1, and the relationship between the mean damage grade and the breakage rate was obtained. For the latter one, the compression strength parallel to the grain was tested to investigate the relationship between the damage grade and the mechanical properties. Results obtained are summarized as follows;
1) All wood posts were conducted to the fence works without any preservative treatments before installation into the ground. More than eighty percent of the installed posts were prepared from sugi (Cryptomeria japonica) and karamatsu (Larix spp.) logs, and their average dimensions were ca. 11 cm for apical diameter, ca. 1.2m for total length and ca. 40 cm for length above ground.
2) The compression strengths parallel to the grain of the installed posts decreased linearly with increasing of grade rating of damage, and they attained to zero when the damage rate reached at grade 5.
3) Assuming that the rapid increase of the breakage rate at 10 percent corresponded to the critical limit of the service lives of installed posts, the values of those were estimated to be about 7.4 and 8.7 years for sugi and karamatsu respectively, from the corresponding values of the damage grade at 3.4.
