Journal of the Japan Society of Erosion Control Engineering
Online ISSN : 2187-4654
Print ISSN : 0286-8385
ISSN-L : 0286-8385
Volume 68 , Issue 3
Showing 1-13 articles out of 13 articles from the selected issue
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Original Articles
  • Tomohiro CHIDA, Takanobu SASAKI, Ryu NODA, Takato INOUE, Toshimasa ...
    2015 Volume 68 Issue 3 Pages 3-10
    Published: September 15, 2015
    Released: March 21, 2017

    In Akita prefecture in Japan, all wood type wooden dam composed only wood members and lag screws has studied and developed from 2001, and it actually have constructed forty in 2011. However, to construct them continuously and to make to diffuse them all over Japan, the cost reduction was required because the costs of them are about two times higher than concrete dam. In previous paper, we proposed the cost reduction method using FEM, and designed the dam where all lag screws on downstream side except the first tier changed round steels as one of optimum design. This dam can decreased the cost 27% and have safety rate 8 for the design load. In this paper, we actually made real-size cost reduction type dam specimen designed previous paper, which called mixed type model in this paper, and conducted horizontal load test. In this test, not round steels but deformed steel bars were used, because the costs of deformed steel bar were far cheep than round steels and deformed steel bars can be obtained briefly at the market. The design method by using FEM was verified by comparing with test results, and the performance of mixed type model was accessed. The test specimen was broken at 84.4 kN by pull-out of lag screw at first stair. These results coincided with the results of FEM very well. Therefore, it was confirmed that the design method using FEM had enough validity and high accuracy and mixed type model specimen had safety rate 8. Additionally, the results of mixed type model specimen compared with the specimen used only lag screw whose test was carried out 2007, it was shown that there is no great difference except failure load.

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  • Tsukasa YOSHIDA, Yoshiharu ISHIKAWA, Yoshihiro TSUJIMOTO, Yoshihisa T ...
    2015 Volume 68 Issue 3 Pages 11-20
    Published: September 15, 2015
    Released: March 21, 2017

    We used a resistograph to measure the deterioration rate of processed wood used in Azekura wooden structures at 15 locations built 5-15 years before the survey. The wood had been subjected to compression treatment and pressureinjected with preservatives (this wood will be referred to hereinafter as “pressurizing-compression-treated wood”). We conducted the same measurement at two locations on non-processed wood that had not been subjected to such treatment. The results revealed that the pressurizing-compression-treated wood had a markedly lower deterioration rate than nonprocessed wood. A major difference in deterioration rates of the main body and wing of the consolidation dams depending on whether the dam is always wet with water (wetness or dryness) has been reported in previous research, but no such difference was observed in the pressurizing-compression-treated wood. Based on these findings, we may conclude that while most of the deterioration in non-processed wood results from rot, in pressurizing-compression-treated wood, which resists rot, the difference in deterioration rate depended on the wetness or dryness of the bodies and wings of the consolidation works will largely disappear. An analysis of the relationship between environmental factors and deterioration revealed that the deterioration rate of pressurizing-compression-treated wood was negatively correlated with annual mean temperature and annual precipitation. We also conducted a freeze-thaw test on the wood, which revealed that increasing the freeze-thaw cycle significantly increases the thickness of the deteriorated part. Based on these results, we can conclude that, as reported in existing literature, deterioration rate is positively correlated with annual mean temperature and annual precipitation in the case of non-processed wood because it is strongly affected by rot and other forms of biodeterioration. However, in pressurizing-compression-treated wood, because wood preservatives minimize the deterioration rate, physical deterioration (by freezing and thawing) has a relatively large impact, and the deterioration rate is negatively correlated with annual mean temperature and annual precipitation.

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Technical Papers
  • Wataru SAKURAI, Ryo SAKAI, Yuki OKUYAMA, Yoshito OGAWAUCHI, Mutsut ...
    2015 Volume 68 Issue 3 Pages 21-30
    Published: September 15, 2015
    Released: March 21, 2017
    The Landslide dams, resulting from the deep-seated landslides that occurred during Typhoon No.12 in September 2011, differed in terms of their internal structure. These differences affected hydrological conditions such as the water level of flooding ponds, their leakage flow rate, frequency of overflow, and severity of erosion. We investigated the relationship between the internal structure of landslide dams and their hydrological and erosion conditions to establish effective countermeasure plans. This was achieved by outlining debris deposition, grain size distribution, and permeability through geological surveys performed in the area of Akadani, Nagatono, and Kuridaira. These landslide dam characteristics were then related to the hydrological and erosion conditions. This study demonstrates that the permeability of a landslide dam has a significant influence on the groundwater level and degree of water level fluctuation within the flooding pond. A thick layer of slide rock masses results in lowered water permeability, which increases the frequency of dam overflow and the corresponding danger of erosion. The risk of erosion is also increased by the accumulation of fine-particle debris at the foot of landslide dams. It is important to understand how erosion-prone sediments are deposited, and what the internal structure of landslide dams is likely to be, such that effective countermeasures can be planned.
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  • Hajime SATO, Tomoyuki ABE, Kazuhiro MINAMINO
    2015 Volume 68 Issue 3 Pages 31-38
    Published: September 15, 2015
    Released: March 21, 2017

    We estimated woody debris flow based on its movement pattern by investigating woody debris along an 11.7-km section of the upper Shiribeshi-Toshibetsu River, in Hiyama District, Hokkaido. The watershed of the lower end of this channel covers 57.1 km2 and contains the Pirika Dam. We measured the size of each piece of woody debris found along the channel, tagged it with numbered tape, and plotted it on a map. We then resurveyed the section and evaluated new woody debris similarly six times after main rain events over 2 years. The proportion of woody debris that moved ranged from 1.9% to 56.1% and increased with the hourly maximum water table at an observatory. The woody debris that moved accumulated mainly on channel bars, and the mean distance moved during the rain events ranged from 275 m to 7532 m. The frequency distribution of the distance moved was an inverse-J distribution. We postulated that obstacles like channel bars were distributed at the same intervals. The “P-value”, defined as the probability that woody debris was captured on each obstacle, decreased as the hourly maximum water table increased. We calculated the yearly woody debris flow to the Pirika Dam using the proportion of woody debris that moved and the “P-value” for 5 years and compared this to the volume of woody debris gathered at the dam. The estimated flow was similar to the volume of gathered woody debris for 2 years, but was underestimated for the other 3 years.

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Discrete analysis and fluid dynamics on sediment disasters and their application examples
Introduction to the countermeasures on landslide dams and its theory inside and outside the country
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