{"created":"2023-06-19T10:30:05.111006+00:00","id":10240,"links":{},"metadata":{"_buckets":{"deposit":"93582147-a123-42c6-917e-1bc0b86255d0"},"_deposit":{"created_by":18,"id":"10240","owners":[18],"pid":{"revision_id":0,"type":"depid","value":"10240"},"status":"published"},"_oai":{"id":"oai:muroran-it.repo.nii.ac.jp:00010240","sets":["41:227"]},"author_link":["57649"],"item_81_date_granted_17":{"attribute_name":"学位授与年月日","attribute_value_mlt":[{"subitem_dategranted":"2020-03-23"}]},"item_81_degree_grantor_10":{"attribute_name":"学位授与機関","attribute_value_mlt":[{"subitem_degreegrantor":[{"subitem_degreegrantor_language":"ja","subitem_degreegrantor_name":"室蘭工業大学"},{"subitem_degreegrantor_language":"en","subitem_degreegrantor_name":"Muroran Institute of Technology"}],"subitem_degreegrantor_identifier":[{"subitem_degreegrantor_identifier_name":"10103","subitem_degreegrantor_identifier_scheme":"kakenhi"}]}]},"item_81_degree_name_11":{"attribute_name":"学位名","attribute_value_mlt":[{"subitem_degreename":"博士（工学）","subitem_degreename_language":"ja"}]},"item_81_description_25":{"attribute_name":"フォーマット","attribute_value_mlt":[{"subitem_description":"application/pdf","subitem_description_type":"Other"}]},"item_81_description_7":{"attribute_name":"抄録","attribute_value_mlt":[{"subitem_description":"侵食や風化作用によって地盤内に形成される空洞は，構造物基礎の支持力低下を導き，構造物の安全性，健全性，耐久性に影響を与える。そのため，空洞が存在する地盤に対する基礎の設計法・対策法の確立が望まれている。特に，このことは化学的風化を受け易く，多くの空洞の存在が確認されている風化岩地盤では重要となる。現在，我が国では，風化岩地盤（カルスト地形）は国土面積の約0.44％を占め，特に沖縄県における海上構造物の建設時に多くの空洞の存在が確認されている。その他，東南アジアに位置するベトナムにおいても風化岩地盤が国土面積の約20％を占めており，人口増加と経済の急速な発展に伴って，そのような地域（特に北部，北中部）での開発が進められている。このような空洞を有する風化岩地盤の支持力動員メカニズムについては，地盤工学的にも未解明な点が多く，研究も限られている。本研究では，風化岩地盤内に埋設した単杭の支持力に対する空洞の影響を定量化し，杭の支持力動員度とそれに起因する空洞破壊のメカニズムを明らかにしている。本研究の目的を達成するために，一連の重力場の模型実験と数値解析を実施している。模型実験では，人工的に作製した空洞の位置を変化させ，風化岩地盤の地盤強度を想定した石膏模型地盤に対して単杭支持力実験を行っている。その後，模型実験の妥当性と杭の支持力動員機構を評価するために，本研究では2次元の離散要素法プログラムを使用した解析を行っている。一連の模型実験では，杭径dに対して空洞の位置を，d，2d，3d，4dに変化させた場合の杭の支持力動員度を明らかにしている。また，一連の数値解析では，連続体解析と比較して，不連続解析（離散要素法）では亀裂伝播が明瞭に再現されること，空洞の崩壊メカニズムが視覚的に表現できることを明らかにしている。これらの結果に基づいて，空洞位置の変化による支持力低減率を定量化し，杭基礎の適用における空洞の影響評価を行っている。また，空洞の存在が支持力に及ぼす影響深さは，杭径の4倍が限界距離であり，それ以上の深さに存在する空洞の影響は無視できること，また，その平面的な概形は，簡易的にダイヤモンド形状で表現できることを示している。研究の総括として，空洞が存在する場合の単杭の支持力設計手法を新たに提案している。","subitem_description_language":"ja","subitem_description_type":"Abstract"},{"subitem_description":"The design and construction of foundations in easily weathered rocks have posed various challenges to geotechnical engineers. One challenge is the formation of cavities in limestone, dolomite due to the chemical weathering process. In Japan, karst topography occupies nearly 0.44% of the land area (1763.73 km2). Specifically, many large-scale caves were found during the geological survey when constructing sea embankments in Okinawa. In Vietnam, it occupies nearly 20% of the land area (approximately 60,000 km2), with some typical regions in the North and Northern Central of the country. Cavities can reduce the bearing capacity of foundations. Therefore, sudden failure is a constant threat to the safety of structures founded on the ground with cavities. This study aims to quantify the influence of the cavity on the pile bearing capacity through reduction factors and gain more insight into the failure mechanism of the area around the pile tip and cavity. A series of model tests was carried out on a small-scale single pile embedded in gypsum rock with predetermined cavities, thereafter, the numerical analysis was conducted. The studied model was simulated by the discrete element method (DEM) using the two-dimensional discontinuous program. Compared with continuum analysis, the DEM can simulate crack propagation. The reduction factor was calculated to quantify the cavity impact on the pile bearing capacity. The experimental and analytical results clearly show that reduction factors decrease with an increase in the depth from the pile tip to the cavity, and the pile capacity is significantly reduced when cavities are located close to the pile tip. The DEM simulation results visualized the cracks that appeared inside the rock mass and the collapse of the cavity roof area, which cannot be seen in the experiment. It revealed that the failure of the cavity roof was mainly caused by the cracks running from the pile tip to the upper corners of the cavity. The study also indicated a critical distance of 4 times pile diameter from the pile tip to the cavity that the influence of cavities to the pile is negligible. Finally, a framework was suggested to apply in pile foundation design in the ground with cavities. Although there were some quantitative differences, the numerical analysis could simulate the same tendency of reduction factors with the experiment. The combination of using experiments and DEM simulations can beneficially examine the influences of cavities on the pile behavior qualitatively and visually.","subitem_description_language":"en","subitem_description_type":"Abstract"}]},"item_81_dissertation_number_13":{"attribute_name":"学位授与番号","attribute_value_mlt":[{"subitem_dissertationnumber":"甲第445号"}]},"item_81_identifier_registration":{"attribute_name":"ID登録","attribute_value_mlt":[{"subitem_identifier_reg_text":"10.15118/00010187","subitem_identifier_reg_type":"JaLC"}]},"item_81_subject_9":{"attribute_name":"日本十進分類法","attribute_value_mlt":[{"subitem_subject":"510","subitem_subject_scheme":"NDC"}]},"item_81_text_12":{"attribute_name":"学位の種別","attribute_value_mlt":[{"subitem_text_language":"ja","subitem_text_value":"課程博士"}]},"item_81_text_14":{"attribute_name":"報告番号","attribute_value_mlt":[{"subitem_text_language":"ja","subitem_text_value":"甲第445号"}]},"item_81_text_15":{"attribute_name":"学位記番号","attribute_value_mlt":[{"subitem_text_language":"ja","subitem_text_value":"博甲第445号"}]},"item_81_text_16":{"attribute_name":"研究科・専攻","attribute_value_mlt":[{"subitem_text_language":"ja","subitem_text_value":"工学専攻"}]},"item_81_version_type_24":{"attribute_name":"著者版フラグ","attribute_value_mlt":[{"subitem_version_resource":"http://purl.org/coar/version/c_970fb48d4fbd8a85","subitem_version_type":"VoR"}]},"item_access_right":{"attribute_name":"アクセス権","attribute_value_mlt":[{"subitem_access_right":"open access","subitem_access_right_uri":"http://purl.org/coar/access_right/c_abf2"}]},"item_creator":{"attribute_name":"著者","attribute_type":"creator","attribute_value_mlt":[{"creatorAffiliations":[{"affiliationNameIdentifiers":[],"affiliationNames":[{"affiliationName":""}]}],"creatorNames":[{"creatorName":"NGUYEN, Thi  Thao  Van","creatorNameLang":"en"},{"creatorName":"グエン, ティ  タオ  バン","creatorNameLang":"ja"}],"familyNames":[{},{}],"givenNames":[{},{}],"nameIdentifiers":[{}]}]},"item_files":{"attribute_name":"ファイル情報","attribute_type":"file","attribute_value_mlt":[{"accessrole":"open_date","date":[{"dateType":"Available","dateValue":"2020-06-08"}],"displaytype":"detail","filename":"A445.pdf","filesize":[{"value":"6.8 MB"}],"format":"application/pdf","licensetype":"license_note","mimetype":"application/pdf","url":{"label":"A445","objectType":"fulltext","url":"https://muroran-it.repo.nii.ac.jp/record/10240/files/A445.pdf"},"version_id":"8588c204-675e-4b49-8ba8-1f6e2278801e"},{"accessrole":"open_date","date":[{"dateType":"Available","dateValue":"2020-06-08"}],"displaytype":"detail","filename":"A445_summary.pdf","filesize":[{"value":"382.4 kB"}],"format":"application/pdf","licensetype":"license_note","mimetype":"application/pdf","url":{"label":"A445_summary","objectType":"abstract","url":"https://muroran-it.repo.nii.ac.jp/record/10240/files/A445_summary.pdf"},"version_id":"897a08d6-8657-4d62-9f80-acaaf18119b8"}]},"item_language":{"attribute_name":"言語","attribute_value_mlt":[{"subitem_language":"eng"}]},"item_resource_type":{"attribute_name":"資源タイプ","attribute_value_mlt":[{"resourcetype":"doctoral thesis","resourceuri":"http://purl.org/coar/resource_type/c_db06"}]},"item_title":"Evaluation of effects of cavities on bearing capacity of a single pile in weathered rock","item_titles":{"attribute_name":"タイトル","attribute_value_mlt":[{"subitem_title":"Evaluation of effects of cavities on bearing capacity of a single pile in weathered rock","subitem_title_language":"en"},{"subitem_title":"空洞が存在する風化岩地盤の単杭の支持力特性とその評価","subitem_title_language":"ja"}]},"item_type_id":"81","owner":"18","path":["227"],"pubdate":{"attribute_name":"PubDate","attribute_value":"2020-06-08"},"publish_date":"2020-06-08","publish_status":"0","recid":"10240","relation_version_is_last":true,"title":["Evaluation of effects of cavities on bearing capacity of a single pile in weathered rock"],"weko_creator_id":"18","weko_shared_id":-1},"updated":"2024-01-22T01:54:41.988969+00:00"}