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第53期 |
都會區之深開挖工程 |
可選購電子書 |
蔡錦松 |
1996/02/01 |
90 |
無庫存
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| PREDICTION OF EXCAVATION-INDUCED SETTLEMENT IN TAIPEI BASIN USING EMPIRICAL METHODS |
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| 謝百鉤、歐章煜 |
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| 台北盆地、深開挖、地表沉陷、經驗公式 |
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| 本文整理現有的各種深開挖引致之地表沉陷的經驗預測方法，以四個觀測良好的實際開挖案例，利用各種經驗預測方法計算沉陷量，再與觀測結果進行比較，確立各經驗預測法之適用性。研究結果發現，無論是凹槽型或三角槽型沉陷型態，Hsieh和Ou的方法均可得到很好的類比。最後本文以有限元素法分析開挖區外地表下不同深度的沉陷情形，並與觀測結果比較，根據分析及比較的結果建議地表下沉陷的預估方法。 |
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| This paper summarizes the current empirical methods for estimating ground surface settlements caused by excavation. The different points among the current empirical methods are discussed. Four excavation cases with well documented measurements are used to compare the suitability of these methods. The present study indicates that Hsieh and Ou's method can give good concordance with field measurements for concave type as well as spandrel type of settlement troughs. Besides, ground settlements at various depths behind the wall are studied using finite element method. Based on the analysis results with the field observations,a tentative method for predicting settlement at various depths is then proposed. |
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| WORKS OF OLD BASEMENT REMOVING FOR DEEP EXCAVATION IN URBAN AREA |
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| 蔡錦松、周立德 |
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| 舊地下室、深開挖工程、都會區 |
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| 都市更新情況下，經常遇到正常深開挖工程進行前，必須將原有建築物遺留下來之舊地下室先行拆除的工作。由於都會區建物緊鄰，拆除工作往往影響到鄰近地盤，甚至造成鄰產損傷。本文主旨在於提供有效的施工方法，並從土壤力學中解壓-再壓的觀念，說明土壤變形之難恢復特性，進而討論拆除工作中，外力支承轉換過程的重要性。文章中並以兩處工地實地完成的成功案例，作為往後工程之參考。 |
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| Removing the basement of old building before normal deep excavation is a commonly met situation today for the development of urban renewing. The disturbance caused by destorying the old basement may affect or even further damage the adjacent properties surrounding due to the congested allocation of buildings. The present paper is to describe useful procedures for construction. The importance of loading support transformation by a neat construction procedure based on the unloading-reloading concept of basic soil mechanics is also included. Two cases are also presented to give examples of successful work for the current concern, and therefore to provide typical procedure that engineers can follow hereafter. |
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| LATERAL EARTH PRESSUR ES DURING DEEP EXCAVATION |
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| 黃南輝、廖建智、范陳柏 |
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| 互制行為、土水壓、深開挖 |
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| 本文根據台北捷運系統新店線 CH219 標中正紀念堂站於開挖施工期間，藉由擋土壁兩側之土、水壓計監測資料回饋推論深開挖過程中，當忽略土壤與擋土壁間摩擦效應時，垂直向壓力將不等於覆土壓， 否則垂直向壓力於主動側將被高估、而於被動側 將被低估。因此在擋土壁設計中必須考量土壤與壁面間之摩擦效應，且針對軟弱至中等堅實土壤時，可假設擋土壁與土壤間之摩擦角等於土壤的內摩擦角。 |
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| This paper evaluates earth pressures recorded during the excavation of C.K.S Memorial Station of Hsintien Line of the Taipei Rapid Transit Systems. The main theme is on wall friction and vertical earth pressures. It can be demonstrated that the assumption normally adopted in the design of retaining structures for braced excavations that the vertical earth pressures equal to the overburden pressures could be erroneous if wall friction is considered. As a result, the vertical pressures on the active side are often over-estimated and those on the passive side under-estimated. Based on field measurements, it is appropriate for soft to medium stiff sites to assume that the angles of wall friction equal to the angles of internal friction of soils in computing the limiting active and passive earth pressures in designing retaining structures of braced excavations. |
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| PRACTICAL CONSIDERATIONS ON DIAPHRAGM WALL ANALYSIS |
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| 謝旭昇、程日晟、蔡宗鍠、楊明洲 |
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| 連續壁設計分析、彈性基礎樑 |
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| 連續壁之設計分析牽涉土壤力學理論、支撐及連續壁之結構行為。但分析之假設狀況常與現場實際情形有所出入，因而導致不合理之設計結果。本文針對連續壁之基本設計假設進行探討，包括分析模式、土壤強度、地盤反力係數、水壓力、超載壓力、支撐預壓等，現場施工控制對連續壁行為之影響亦有所提及。基本上連續壁之設計仍須倚賴經驗，純理論之分析結果易生錯誤。 |
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| Design and analysis of diaphragm wall requires knowledge on soil mechanics as well as behaviors of strut and wall. The design is generally based upon assumptions that deviate a lot from practice, which may lead to erroneous results. This paper discusses the nature of a few design assumptions, including analysis model, soil strength, modulus of subgrade reaction, water pressure, surcharge loading, preload of struts,etc. The effects of construction control on the behavior of diaphragm wall are also addressed. Basically, the design must rely heavily on experience, or else it may be completely incorrect. |
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| A NOTE ON THE MODULUS OF SUBGRADE REACTION FOR RAFT FOUNDATION DESIGN |
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| 謝旭昇、程日晟 |
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| 筏基、地盤反力係數 |
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| 目前大樓基礎大部份採用筏式基礎，而地盤反力係數為一重要之設計參數。基本上地盤反力係數並非純粹由土壤性質決定，設計上須同時考慮土壤及結構之勁度以為選擇之基準。本文列舉現行決定地盤反力係數之各種方法，並以案例顯示其間之差異。本文亦討論連續壁及結構勁度對整體分析之影響，作者並依本身之設計經驗提供一組地盤反力係數值以供參考。但在目前地盤反力係數值仍位有定論之狀況下，筆者建議筏基設計時進行必要之敏感度分析。 |
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| Most of the current high-rise buildings use raft foundation as their main foundation system, and the modulus of subgrade reaction (Ks) is considered as one of the essential design parameters. Basically, modulus of subgrade reaction is not just a soil parameter, it is affected by the structural stiffness as well. This paper lists various approaches for the selection of Ks；an example is provided for comparison purpose. The effects of diaphragm wall and structural stiffness is addressed, and the authors also recommend a set of Ks values for reference. For critical structural design, it is suggested that a sensitivity study on Ks be always carried out. |
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| UNDERPINNING FOR PIER A15 OF CHUNGHSIAO BRIDGE OF TAIPEI |
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| 蘇信淵、彭嚴儒、朱 旭、陳鴻濤 |
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| 托底、地盤改良、荷種轉移 |
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| 台北市忠孝橋橋墩A15的基礎原係由16支直徑0.5公尺、長度35公尺之鋼管樁支撐，由於捷運隧道路線通過該橋墩下方，必須於潛盾隧道通過前對橋墩先進行托底工程及切除北側之6支鋼管樁。托底作業期間橋墩之容許沉陷量為10公厘。主要工程項目包括設置直徑1.2公尺、長度50公尺之基樁5支及深2公尺、寬1.5公尺之支承梁。並於新設之托底支承梁之樁及帽梁施作時，開挖深約8公尺。橋墩荷重轉移作業期間採用自動監測系統即時監控轉移過程。監測項目計有基樁、帽梁、千斤頂及橋墩之位移量，千斤頂荷重及以鋼筋計監測基樁荷重。觀測結果顯示轉移期間千斤頂最大總荷重達483噸，最大衝程約3公厘，基樁最大沉陷約0.2公厘。整個荷重轉移過程中，橋墩隆起約1.5公厘。而捷運南港線下行線潛盾通過期間，橋墩僅產生約1公厘之沉陷。 |
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| Pier A15 of Chunghsiao Bridge is founded on 16 steel pipe piles with a diameter of 500mm. Six of them blocked the way of two stacked tunnels of the Taipei Rapid Transit Systems and had to be removed before the shield machine passed under the pier. The bridge structure is a continuous prestressed beam. The settlement of the pier was limited to 10mm. A pit was made first to expose the pile cap and to provide sufficient headroom for subsequent operations. Five cast-in-place concrete bored piles were installed and cast into a load-transfer slab. The load from the bridge was transferred to these new piles by jacking the pile cap against this transfer slab before the cutting of the old piles. A total jacking force of 483 tones was applied. After all these six piles were cut, the transfer slab was structurally connected to the pile cap to form a composite cap and the operation was then completed. Instrument readings indicate that the pier heaved up by an insignificant amount of 1.5mm during underpinning. The settlements of new piles were only 0.2mm. The lower tunnel has been completed and the settlement of the pier during the passing of the shield machine was only 1mm. |
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| INFLUENCE OF DEEP EXCAVATION YO ADJACENT SHIELD TUNNEL IN CLAY SOILS |
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| 余明山、賴慶和、楊清源 |
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| 深開挖、潛盾隧道、有限差分法、雙曲線模式 |
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| 本文主要是以有限差分法分析程式FLAC，配合FLACish語言修改其內建之應力一應變模式，使其能以雙曲線模式模擬土壤之非線性行為，從而建立深開挖之分析模式，藉以探討軟弱粘土層中之深開挖工程對鄰近潛盾隧道應力與變形之影響，並評估保護措施之有效性，提供日後類似工程規劃之參考。 |
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| The authors have incorporated hyperbolic model into finite differential computer program FLAC to make it possible to simulate non-linear behavior of soils, and subsequently, to develop a deep excavation analysis model. A chosen case of Taipei tunnel affected by adjacent excavation is evaluated by the above-mentioned to find the possible changes in stress and deformation of the adjacent shield tunnel during deep excavation. Effectiveness of some protect measures are also assessed in the paper for future engineering practices. |
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| PRACTICE OF DRILLING SUPERVISION |
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| 施國欽 |
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| 鑽探、地質調查 |
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| 鑽探為地質調查中最常用且最直接的方法，鑽探品質固然與鑽探設備及鑽探師傅的 技術有闕，但鑽探督導者的專業素養及鑽探督導工作的嚴格執行才是最主要的因素，由於鑽探督導工作常由資淺工程師負責，因此常有無法掌控品質及不知所措之窘境。有鑑於此，筆者僅以個人的經驗，敘述鑽探設備及步驟，提供作業程序檢查表期能掌握鑽探品質，避免疏漏，並指出鑽探作業常見之缺失供工程界參考。 |
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| Drilling is one of the most popular techniques of site investigation. Its accuracy is fundamental to a successful site investigation program. The drilling supervisor should have a sound knowledge of construction methods and design process and be familiar with drilling techniques as well (e.g. their limitations and ways to interpretation). Unfortunately, in most cases, a junior engineer instead of a senior one is sent to the site as the supervisor. Therefore, it is highly possible that accurate and useful results of underground conditions may not be obtained. Based on the author's experiences on site investigation, checking lists concerning the scope and process of drilling are presented in this paper. |
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