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研究生: 蘇嘉瑋
Chia-Wei Sue
論文名稱: 台北盆地衝鑽式地錨破壞機率研究
Calibration of Reliability-based Resistance Factors for Soil Anchors in Taipei Basin
指導教授: 卿建業
Jianye Ching
口試委員: 廖洪鈞
Hung-Jiun Liao
劉家男
LIU, Chia-Nan
學位類別: 碩士
Master
系所名稱: 工程學院 - 營建工程系
Department of Civil and Construction Engineering
論文出版年: 2008
畢業學年度: 96
語文別: 中文
論文頁數: 143
中文關鍵詞: 地錨拉拔力可靠度安全係數
外文關鍵詞: alluvial soils, pullout test, reliability-based design, resistance factor
相關次數: 點閱:183下載:5
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  • 在台北盆地,多數地錨的施工都是先以旋轉套管鑽孔,再以水將殘餘土以高壓沖出。這樣的施工過程常使實際的鑽孔直徑比套管直徑大,且鑽孔壁常呈現不規則的形狀。這兩項因素都有利於提升地錨拉拔力,然而提升程度有多少常常是不確定的。為了求保守,一般計算設計拉拔力時都不考慮這兩項因素。在這樣保守的計算下,大部分規範(如FIP 1982)仍採用相當高的安全係數(安全係數 = 3),驗證此安全係數是否過於保守,是本研究的主要議題。本研究根據台北盆地的46根地錨現地實驗資料,經過嚴謹的全機率分析,得到以下的結論:安全係數=3所對應的設計破壞機率小於10-4;若設計的地錨為暫時性結構,這樣的設計破壞機率過於保守。若採用設計破壞機率10-2,所需要的安全係數約在0.9到1.8之間;若採用設計破壞機率10-3,所需要的安全係數約在1到2.4之間。這比規範所採用的安全係數小了許多。


    The goal of this research is to calibrate the reliability-based resistance factor of flush drilled soil anchors for their ultimate pullout capacities based on in-situ anchor pullout test data in the alluvial soil underlying the Taipei basin. Efforts are taken to quantify the uncertainties with a full probabilistic analysis approach. The resistance factor is calibrated based on the in-situ test results of 46 anchors with a rigorous theoretical approach which constructs the relationship between the resistance factor and failure probability. With this relationship, the reliability corresponding to the code regulation can be verified. From the results of the analysis, it is found that the borehole enlargement due to the flush drilling is quite significant: the actual diameter of the fixed anchor end may be much larger than the nominal diameter of the drilling casing. Consequently, the safety factor of three recommended by most anchor codes is found to be too conservative. The results should be valuable for reliability-based design of flush drilled soil anchors in the Taipei basin.

    中文摘要 I ABSTRACT II 致  謝 III 目  錄 IV 表 目 錄 VII 圖 目 錄 VIII 符號表 X 第一章 緒論 1 1.1 研究動機及目的 1 1.1.1 地錨設計上使用安全係數的問題 1 1.1.2 阻抗因子與安全係數之關係 3 1.2 研究目標 3 1.3 研究方法 5 1.4 論文架構 6 1.5 研究流程 7 第二章 文獻回顧 8 2.1 地錨的形式 8 2.1.1 砂土層中的地錨錨錠段 9 2.1.2 黏土層中的地錨錨錠段 10 2.1.3 規範裡的安全係數 11 2.2 貝氏分析 12 2.2.1 貝氏模型更新與一般模型更新的差異 14 第三章 資料庫 16 3.1 現地最大測試拉拔力 16 3.2 測試地錨附近的土壤剖面圖 18 3.3地錨的結構型態 23 3.3.1 標稱鑽孔直徑 24 3.3.2 地錨工程施做流程概述 25 第四章 模型建置 28 4.1 一般拉拔力模型的建置 28 4.2 地錨標稱拉拔力模型 30 4.3 比較真實拉拔力與預測拉拔力 31 4.3.1 真實拉拔力與預測拉拔力之比較結果與討論 34 4.4 折減係數 36 4.5 將折減係數置入拉拔力模型 39 4.6 不確定性參數模型 40 4.6.1 量化不確定性參數 42 4.6.2 不確定土壤參數與不確定模型參數 42 4.7 建立事先聯合機率密度函數前的假設 43 4.7.1 地錨中的折減係數α的假設 43 4.7.2 有效直徑Dj的假設 45 4.7.3 土壤單位重γ的假設 45 4.7.4 不排水剪力強度與有效覆土壓力比β的假設 46 4.7.5 砂土摩擦角φ的假設 47 4.8 擴孔因子ρj 48 4.9 所有不確定參數的集合事先機率密度函數 49 第五章 研究方法 51 5.1 破壞機率關係式 51 5.2 阻抗因子與破壞機率關係式的推導 52 5.3 取樣{G1,…,GN} 54 5.4 Metropolis演算法 56 5.5 Gibbs─Metropolis混合演算法 60 5.6 隨機取樣法應用於貝氏模型更新 63 第六章 分析結果與驗證 67 6.1 機率分析模擬的樣本結果 67 6.2 驗証研究分析結果 70 6.3 阻抗因子與目標破壞機率的關係 71 6.3.1 討論設計模型為Cα=0.0025之阻抗因子與目標破壞機率的關係 72 6.3.2 討論設計模型為Cn之抵抗因子與目標破壞機率的關係 76 6.3.3 研究成果探討 79 6.4 由長徑比推估預測拉拔力 83 第七章 結論與未來展望 85 7.1 結論 85 7.2 未來展望 87 參考文獻 88 附錄A 土層細部資料 92 附錄B 拉拔利資料 97 附錄C 程式碼 107

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