A Study of Engineering Behavior on Deep Excavation Adjacent to Different Types of Foundation

本研究使用PLAXIS 2D有限元素程式探討鄰近不同基礎型式開挖工程之相關力學行為，並且以臺中市卵礫石層為例，模擬在兩種不同基礎型式下承受相同的載重，分別為筏式基礎及聯合基腳。相同地質條件：地表下1.5m部分為回填砂土及卵礫石偶夾雜物層，其地表下1.5m之後的部分為卵礫石層，地下水位設在地表下15m之後。依擋土設施與基礎邊緣距離分為2m、4m及6m，總共六種案例。 研究顯示：(1)開挖工程與基礎之距離由6m減至4m，再由4m減至2m，探討這兩段距離變化對於擋土設施影響，其發現擋土結構剪力、彎矩在一定的距離變化下，聯合基腳的剪力、彎矩增加幅度較筏式基礎明顯(2)開挖工程對基礎之遠近、基礎形式影響下，對於水平支撐軸力來說，在相同距離變化4m減至2m的軸力變化較6m減至4m來的明顯(3)鄰近基礎之深開挖影響，在基礎之差異沉陷的部分探討發現，不論距離開挖工程之遠近，筏式基礎之差異沉陷皆來的比聯合基腳小，並隨著距離開挖工程愈遠，基礎之差異沉陷、擋土設施變形也跟著縮小(4)本研究之模型為剖半分析，開挖底部皆有隆起現象，在一樣承受相同的載重之下，其對稱中心點不論基礎是不同型式或是距開挖面之遠近，對於底部隆起現象並不明顯之影響。Such as gravel of Taichung city,this study aims at the relevant behavior of excavation adjacent to different types of foundation that using the PLAXIS 2D finite element program. Respectively, raft foundation and continuous footing , it imitates two types different of foundations , bearing same of loading. The geological is same: the surface sand is 1.5m of thickness , the lower is gravel and groundwater is located 15m under the surface. According to distance between the retaining facilities and edge of base, it is divided into 2m,4m and 6m. Total six cases are carried for analysis. From the analyzed results , it show that (1).When the distance between the retaining facilities and foundation edge is from 6m reduced to 4m and from 4m reduced to 2m. It explores that the effect of these two distance changes on retaining facilities. It was found that continuous footing shear and bending moment of retaining structure are clearer than raft foundation`s under distance of same.(2).Influence of distance between the retaining facilities and types of foundation , the axial force of horizontal strut change that from 4m reduced to 2m is clearer than from 6m reduced to 4m.(3).Engineering influence on deep excavation adjacent to foundation found that the foundation produces differential subsidence. No matter what distance between the retaining facilities and foundation edge, differential subsidence of raft foundation is smaller than continuous footing one.As the distance from the excavation project is further away, the differential subsidence of foundation and deformation of retaining facilities are reducing.(4). The model of this study is a half-section analysis, in which the bottom of the excavation has a bulging phenomenon. Bearing the same load, the center point of the half-section structure is different types of foundations or the distance from the excavation area, and the bottom bulge. The phenomenon of bottom swell that have a noticeable effect.目錄 摘要 i Abstract ii 表目錄 v 圖目錄 vi 第一章 緒論 1 1.1前言 1 1.2研究動機與目的 2 1.3研究方法 3 1.4研究內容 4 第二章 文獻回顧 5 2.1卵礫石層之工程性質 5 2.2淺基礎之介紹 7 2.2.1淺基礎之設計 7 2.2.2土壤中淺基礎之Terzaghi承載力理論分析 12 2.3開挖工程之行為探討 14 2.3.1開挖對鄰近建築影響 14 2.3.2台中地區卵礫石層之擋土設施型式 19 2.3.3深開挖擋土壁體之特性 22 2.4數值分析-有限元素法 23 第三章 分析方法 25 3.1分析軟體之介紹 25 3.1.1輸入(Input)階段 25 3.1.2計算(Calculation)階段 26 3.1.3輸出(Output)階段 27 3.2網格生成 28 3.3 PLAXIS程式功能之介紹 28 3.4材料參數之設定 30 第四章 範例研究分析 33 4.1前言 33 4.2研究範例 33 4.2.1研究內容之介紹 33 4.2.2案例模型之介紹 34 4.2.3材料之參數 38 4.2.4研究之分析步驟 41 4.3研究範例一 42 4.4研究範例二 51 4.5研究範例三 60 4.6研究範例四 69 4.7研究範例五 78 4.8研究範例六 87 4.9研究範例分析結果比較 96 第五章 結論與建議 101 5.1 結論 101 5.2建議 103 參考文獻 10