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To get useful informations for design and working methods of coming forest road, we investigated the actual conditions of land slide of cutting slope of forest roads in MIYAZAKI prefecture, which rece...ived great damages by concentrated heavy rains in August, 1971 and from June to July, 1972. In this report, we analyzed relations between land slide of cutting slope and working factors, slope exposure, established year and geological features in actual forest roads, and rearranged these results. The results obtained were followings. 1) It seemed that land slide caused by several hundreds millimeters from the beginning. But, we could not understand when or how much precipitation caused land slide. 2) Based on geological map, geological features in this region showed the distribution of sandstone (ss), clay slate (cl), sandstone and clay slate (cls) alternatingly, and the intrusion of diabase and basalt (Db) here and there. However, we must investigate soil or geological features of earth surface layer in detail concerning land slide of forest road. 3) Land slide of cutting slope occurred concentrically during 1-4 years after establishment of forest road, and about 5 years after cutting slope condition became stable. 4) To explain the effect of cross-sectional diagram and gradient of ground surface, we introduced index designated failure percentage. It could be expressed by means of next equation. Failure percentage = $\frac{Frequency of land slides (%)}{Frequency of standard points (%)}$ When failure percentage was equal to 1, we called the value of each factor at that time critical point. The critical points of each factor were as follows. Length of cutting slope about 5 m Gradient of ground surface about 24-46°Cutting area about 10 $m^2$ If each factor exceeded these values, land slide of cutting slope easily occurred. 5) In each forest road, there was no definite preponderance of land slide occurrence on any particular slope exposure.続きを見る
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緒論 I 調査地域の概況 II 崩壊調査結果 1) 路線 2) 開設年 3) 地質 III 崩壊発生比 1 発生頻度分布 2 崩壊発生比 1) 切取法面長 2) 地盤傾斜角 3) 切取面積 4) 斜面方位 5) 開設年 6) 地質 IV 結果および考察 引用文献 Resume
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Mendeley出力
KJ00005470555