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沈床式防波堤の現状とその挙動観測結果の解析
https://fra.repo.nii.ac.jp/records/2007782
https://fra.repo.nii.ac.jp/records/200778225aadb12-27a1-419c-82c5-ff96e4cba6b7
| アイテムタイプ | 紀要論文 / Departmental Bulletin Paper(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2024-06-18 | |||||
| タイトル | ||||||
| タイトル | 沈床式防波堤の現状とその挙動観測結果の解析 | |||||
| 言語 | ja | |||||
| タイトル | ||||||
| タイトル | The Present State and the Analysis of Field Observation of the Breakwaters with the Reinforcing Steel Beams | |||||
| 言語 | en | |||||
| 言語 | ||||||
| 言語 | jpn | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_6501 | |||||
| 資源タイプ | departmental bulletin paper | |||||
| アクセス権 | ||||||
| アクセス権 | metadata only access | |||||
| アクセス権URI | http://purl.org/coar/access_right/c_14cb | |||||
| 著者 |
大槇, 正紀
× 大槇, 正紀 |
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| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | The breakwaters with the reinforcing steel beams in the rubble mound have been constructed for the last two decades at harbors and fishing ports in Japan. The present state and the subjects of the design and construction methods of such breakwaters are summerized at the beginning of this paper. The numerical method is proposed focussing to the estimation of both settlement and bending stress of the reinforcing steel beams. By using this method, two actual and several provisional case studies are carried out and the behavior of the settlement and bending stress of the reinforcing steel beams are investigated. The following feature and problems are pointed out from the results of the reviewing the design and construction methods of the breakwaters reinforced by the steel beams. 1) In order to estimate the coefficient of soil reaction, k, in the vertical direction from the blow counts, N, of the standard penetration test, the following relationships have been used. k=12 α∙N∙Bᵥ⁻⁰∙⁷⁵ ….. (1) k=0.20 N ….. (2) k=0. 15 N ….. (3) where a is equal to one or two corresponding to the ordinary and seismic states respectively and By denotes the loaded area. Taking into account the empirical relationship between the blow counts N and the unconfined strength qᵤ of cohesive soil as N = 8qᵤ then eqs. (1), (2) and (3) are rewritten as follows respectively. k=96 α∙qᵤ∙ Bᵥ⁻⁰∙⁷⁵ ….. (4) k=1.6 qᵤ ….. (5) k=1.2 qᵤ ….. (6) Eqs. (1), (2) and (3) give approximately the same results of the coefficient k of soil reaction and well correspond to the k value estimated from the observed bending moment of the steel beams by the soil reaction method. On the other hand, it seems that eqs. (4), (5) and (6) overestimate the coefficient k. 2) From the review of already constructed breakwaters with the reinforcing steel beams, the following facts are presented. In order to propagate the stress induced by the external load through the steel beams to the ground, it is necessary that the rubble mound or sand layer are thicker than (4~5)×0.87 (P-B) where P and B denote the pitch and the width of the installed steel beams respectively. The shoulder width of the rubble mound is one or two times the length of the reinforcing steel beams. The length of the reinforcing steel beams is 1.5~3 times the width of the caisson installed on the rubble mound An analytical procedure of the steel beams used as the reinforcing mattress under the breakwaters is developed which is formulated by combining the soil reaction method with the theory of one dimensional consolidation of soil. Two basic equations available are discreted by the Galerkin method to be able to apply numerically to the various boundary conditions. The present analytical procedure is applied to two breakwaters of the fishing ports where the observed results of the settlement of breakwaters and the bending stress of the reinforcing steel beams in the field are available. Realistic representations of the breakwaters in the connection with the settlement and the bending stress are available by taking into account the reasonable distribution of the volume compressibility of soil. The present two case studies suggest the following facts conclusively. 1) The distribution of the bending moment of the reinforcing steel beams are sensitive to the factors such as the ground conditions, the loading conditions and the rate of construction. 2) In order to analyse accurately the bending behaviour of the beams by the present procedure, it is necessary to use the reasonable distribution of the volume compressibility of soil taking into account two dimensional deformation pattern of ground including the lateral flow of soil. 3) The settlement of the breakwaters is reasonably estimated by using the volume compressibility of soil obtained from the standard oedometer tests of soil specimen sampled from the field. The present analytical procedure is also applied to several provisional sections of breakwaters with the reinforcing steel beams in order to study numerically the effects of ground improvement and the reinforcing steel beams. The following points are conclusively obtained from these numerical analysises. 1) In the case of the breakwater without ground improvement, the settlement is not so much influenced by the length of steel beams but the inclination of steel beams increases with an increase in the length of beams. The maximum absolute value of the bending stress of the beams increases with an increase in the length of beams and approaches to a contant value for large length of the beams. In the case of the breakwaters constructed on the improved ground by the compacted sand piles, the bending moment of the steel beams is hardly influenced by the length of beams. 2) By improving the soft ground by the compacted sand piles, it is possible to decrease the settlement and the absolute value of bending stress of the beams. In particular this effect is remarkable by using such shape of ground improvement as the degree of stress concentration by the external load is reduced. 3) The degree of concentration of stress induced at the boundary between treated and untreated parts of the ground increases with a decrease in the improved width of soil foundation. | |||||
| 言語 | en | |||||
| 書誌情報 |
ja : 水産工学研究所研究報告 en : Bulletin of National Research Institute of Fisheries Engineering 巻 8, p. 81-112, ページ数 32, 発行日 1987-03 |
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| 出版者 | ||||||
| 出版者 | 水産工学研究所 | |||||
| 言語 | ja | |||||
| 出版者 | ||||||
| 出版者 | National Research Institute of Fisheries Engineering | |||||
| 言語 | en | |||||
| ISSN | ||||||
| 収録物識別子タイプ | PISSN | |||||
| 収録物識別子 | 0388-9718 | |||||
| 書誌レコードID | ||||||
| 収録物識別子タイプ | NCID | |||||
| 収録物識別子 | AN00332937 | |||||
| 情報源 | ||||||
| 識別子タイプ | Local | |||||
| 関連識別子 | nrife_k_8_81 | |||||
| 関連サイト | ||||||
| 識別子タイプ | URI | |||||
| 関連識別子 | https://agriknowledge.affrc.go.jp/RN/2010370934 | |||||
| 言語 | ja | |||||
| 関連名称 | 日本農学文献記事索引(agriknowledge) | |||||
