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余明山 |
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「軟弱地盤」廣義之定義係指不符合工程需求,如穩定性不足或可能產生過大沉陷或變形之地盤。通常所謂的軟弱地盤是指堆積在山谷、湖沼地以及下游之沖積平原等自然形成之軟弱沖積土層,以及藉由埋填、回填等所堆積成之軟弱人工地盤,如山谷棄土區、港灣回填區或濱海抽砂造陸區等。由於軟弱地盤通常具鬆軟、高孔隙比、高含水量、低強度、易於壓縮與變形、受地震影響顯著等特性,故於工程開發前應確實掌握軟弱地盤之工程特性,再依據工程需求採取適當之工程處理對策,始可確保施工安全與工程構造物長期之穩定與機能。 軟弱地盤可概分為軟弱土壤與易液化土壤兩種特性,工程處理之對策,除改變上部結構載重之分配與選用適當之基礎型式外,地質改良為較直接有效之方法。地質改良所處理的對象大多數均具有不均勻性與不確定性,尤其是台灣西海岸及東部蘭陽平原之沖積層構造,此類狀況更形顯著。規劃設計時若未能確實瞭解地層之整體情況與夾層變化,地質改良效果將難以掌握,因此細部設計前之詳細地質調查與試驗甚為重要。地質改良工法之設計,由於大部份均無完備嚴謹之理論基礎,故實務上多憑經驗設計法,惟影響改良效果之因素甚多,以此方式所進行之設計,未必能確實掌握所有影響因素,因此正式施工前藉由前導試驗(Pilot Test)驗證設計理念之正確性,及確認設計之合理性為一極重要之步驟。此外,施工中之監測及施工後之改良成效檢驗亦屬必要之程序,以確實掌控改良地層之行為變化回饋設計,並掌握施工品質之變異性,實施必要之補強改良,以達設計改良目標需求。 隨著都市人口與經濟之快速成長,都市大面積土地取得困難,民眾環保意識抬頭,大型公共工程、工業區及新市鎮之開發,為取得大片建設土地,常須以填土方式將低窪區或海埔地填平墊高,以取得建設用地,如截彎取直後之基隆河廢河道,台北捷運北投機廠、彰濱工業區、雲林離島式基礎工業區等,甚或利用已填埋完成之棄土區、灰塘新生地進行工程基地。如何確保開發工程之穩定與安全,有效解決回填造地所衍生的相關大地工程問題如地層壓密沉陷、回填土壤液化、軟弱地盤承載力不足等問題,均是軟弱地盤開發之重要課題。 為此,地工技術本期專輯即以「軟弱地盤與工程處理」為題,邀集國內學術界與產業界等專業人士,針對台灣地區軟弱地盤之工程特性研究、軟弱地盤改良工法與施工案例、設計規範及國外新技術應用等作專輯探討,期能提供讀者對台灣地區軟弱地盤特性與工程處理有更深入之認識,對國內軟弱地盤改良技術之提昇有所助益。本專輯共收錄八篇論文,每篇均值得閱讀參考,以下逐一概略介紹。 本期第一篇為李維峰博士等五人所發表之「台灣低塑性粉土工程性質之研究」,該文係利用自行研發的Gel-Push取樣器,取得高品質原狀低塑性粉土試體,藉由一系列的土壤動態工程特性試驗及內沖蝕試驗,探討土壤中低塑性細料含量對土壤液化特性與內沖蝕之影響,使吾人得以更瞭解台灣低塑性粉土之工程特性,而作者更希望借由本文的提出,喚醒地工界對於土壤取樣技術與試驗的重視。 第二篇為趙紹錚博士等人所撰寫之「宜蘭地區軟弱地盤工程特性」,該文藉由介紹蘭陽平原地體構造、宜蘭縣大地工程分區、蘭陽平原整體特性、及土壤液化初步分析等課題,說明宜蘭地區近年來與軟弱地盤工程特性有關之研究成果,冀能提供於該地區進行工程規劃設計施工時之參考。 第三篇為黃俊鴻博士等人所發表之「台中火力發電廠灰塘擠壓砂樁工法改良成效評估」,該文針對擠壓砂樁工法應用於台中火力電廠灰塘煤灰改良之案例,藉由改良前後之現地探查試驗結果及施工監測資料,探討擠壓砂樁施工過程對煤灰地層所激發之超額孔隙水壓行為與側向變形,以及施工後的改良成效。相信本文有助於讀者對煤灰大地工程性質之認識,並對擠壓砂樁改良煤灰地層之成效,以及施工過程對周邊環境影響得以深入瞭解。 第四篇是由張志勇先生等人所撰寫之「濱海軟弱土壤的地盤改良工法-以越南某鋼廠為例」,內容介紹國內台塑集團在越南興建之煉鋼廠廠區地盤改良設計與前導試驗案例,文中提及之動力排水壓密工法、高真空擊密法及真空預壓工法等,在國內尚屬罕見,或可提供讀者在設計濱海相軟弱地層改良時更多之工法選擇。 第五篇是吳建閩先生等人所發表之「真空預壓之設計與施工」,該文介紹國內尚未見有施工實績之真空預壓工法,對於真空預壓工法之設計考量與施工程序有詳盡之說明,並附有多幅施工照片,有助於讀者對真空預壓工法改良機理與施工細節之瞭解,不同於國內慣用之堆載預壓工法,真空預壓工法係藉由大氣壓力進行預壓,無需大量堆載土方,可減輕對環境的污染與衝擊,是值得加以推廣之壓密排水工法。 第六篇為林宏達教授等人所撰寫之「沉積土層將開挖有限土體引致之土壓分析與案例探討」,該文針對近接施工中常遭遇之新建擋土結構與既有建等物地下室間存在之有限寬度土體所引致之土壓力,提出一套量化的分析方法,建立有限土體土壓力與距牆比之關係,並以實際案例探討驗證,可供研析有限土體深開挖問題之參考。 第七篇為黃俊鴻教授等人所發表之「本土HBF土壤液化評估方法之不確定性」,該文介紹作者所發展之雙曲線函數(HBF)簡易評估法之模式不確定性與精確度改善研究成果,相關概念說明清晰,可提供讀者更深入且正確之認知。HBF法目前已列入最新版之「公路橋樑耐震性能設計規範草案」,期盼國內工程師能多加使用,累積經驗逐步改善,以達到設計規範本土化之目標。 第八篇為黃富國博士等人所撰寫之「斷層帶上設置掩埋場之相關法規研析與退縮距離探討」,該文首先彙整國內外相關法規與文獻進行研析,並對國內外案例資料進行探討,最後綜整專家會議之結論,提出法規修改之建議,供爾後修訂相關法規之參考。 除上述八篇與專輯主題相關之文章外,尚納入工程地質研討會專欄,本期由台北科技大學材料與資源系詹尚書先生等人,報導參與變質岩與隧道工程地質研討會之活動經過與內容,文中除對壯麗之地形地質景觀等作解說外,並對蘇花公路與北迴鐵路隧道工程施工所遭遇之工程地質問題詳加說明,並附上精美的彩色照片,讓無法參與者,讀後也可領會其中的知性與樂趣。 最後,編者衷心感謝所有作者於百忙之中撰稿共襄盛舉,無私的分享研究成果與工作經驗,也感謝所有參與審稿委員提供寶貴意見與悉心指正,讓文章內容更臻完備,並提高論文的可讀性。 |
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陳樁亮 |
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承蒙「地工技術研究發展基金會」編輯委員會的推薦及方總編輯的邀請,由拙筆代為撰寫此篇贈言,實感榮幸之至。 本期「地工技術」以軟弱地盤為主題,除探討軟弱地盤的相關施工技術外,亦期藉由廣泛且深入的施工案例說明,讓讀者了解臺灣及海外各地區軟弱地盤的特性及其採用工法在此類地盤的施工成效。論文主題涵蓋高鐵沿線軟弱粉土工程特性、宜蘭地區軟弱地盤工程特性、台中火力電廠灰塘擠壓砂樁工法改良成效、擠壓砂樁應用於泥炭土及淤泥質地盤改良、濱海軟弱土壤的地盤改良工法、沈積土層深開挖有限土體引致之土壓力分析、鄰近捷運隧道深開挖施工地盤改良、真空壓密工法之設計與施工..等,內容精彩實用。 軟弱地盤普遍存在於人類生活週遭,從繁華擁擠的都會區到偏僻無人的濱海地區,大地工程人員都可能面臨於軟弱地盤施工所帶來的挑戰。如本期中鄰近捷運隧道深開挖施工地盤改良案例,係都會區常見之狀況。在都會區施工,不但要面對先天軟弱地盤的課題,要維護既有的捷運隧道安全,尚需處理都會區擁擠的交通問題並設法降低施工噪音,同時避免水及空氣的汙染。偏僻無人的濱海地區儘管毋須面對擁擠的交通問題,不用嚴格控管施工噪音,但環保單位對水及空氣汙染的稽查,卻不會因地處偏遠而鬆懈。而地下水含有鹽分的軟弱地盤,也可能是濱海地區大地工程的另一種課題。 個人投身臺北都會區捷運工程建設20餘載,從最初的木柵線、淡水線捷運建設到目前積極施工中的松山線、信義線、桃園機場聯外捷運線臺北市區段及環狀線,軟弱地盤問題一直如影隨形。但隨著設計經驗的累積及施工實務的回饋,我們對臺北盆地軟弱地盤的了解越來越深入,也越能掌握其工程特性。現今臺北都會區的軟弱地盤施工對我們而言,已經不是困難的問題。其代表的意義是,透過前人經驗的累積與知識的傳播,如今大地工程界已能掌握臺北都會區軟弱地盤的特性,相關施工也就隨之更安全,而「地工技術」就是當今臺灣大地工程經驗累積與知識傳播的最佳平台。期望未來大地工程界的先進們,能善用此平台踴躍投稿,不吝分享您的經驗與know-how。讓更多人能了解您的努力與付出,讓更多大地工程的經驗、訣竅與知識,能藉由「地工技術」廣為傳播與分享,讓大地工程的規劃設計與施工安全能持續精進。 |
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Study on the Engineering Properties of Non-Plastic Silty Sand in Taiwan |
李維峰 石原研而 陳俊吉 陳景文 張浼珣 |
低塑性粉土質砂,gel-push取樣器,flexible wall pin hole試驗儀,土壤液化, |
本文主要探討當土壤中含低塑性細粒料含量對土壤液化特性與內沖蝕性質之影響,本研究利用Gel-Push取樣器取得高品質原狀低塑性粉土試體,並開發Flexible Wall Pin Hole試驗儀探討低塑性粉土之內沖蝕性質,研究成果顯示,當土壤中含有大量低塑性細粒料時,土壤受地震力作用仍會産生土壤液化行為,且低塑性細粒料含量與土壤孔隙比為影響其液化阻抗之重要因素,而擾動效應亦使低塑性粉土之液化阻抗與液化後體積應變産生顯著影響。土壤之低塑性細粒料含量與有效覆土應力愈高時,土壤之抗內沖蝕能力愈低,而增加土壤之相對密度,可有效提高土壤之抗內沖蝕能力。 |
In this paper, a research project aiming to study liquefaction potential and internal erosion property of non-plastic silty sand is introduced. Gel-Push sampler was used to obtain high quality undisturbed specimens. Flexible Wall Pin Hole test instrument and applied test method were developed to investigate the internal erosion properties of this kind silty sand. Results of this study conclude that soil liquefaction would occure in non-plastic silty sand deposits even with high non-plastic fines content. Both fines contents and void ratios have deterministic influences to the cyclic resistance of such silty sand material. Most importantly, disturbance effect would have great influence on cyclic resistances and post liquefaction volumetric strains of non-plastic silty sand. The internal erosion resistance of silty sand is decrease with increase of non-plastic fines content and confining pressure. Increasing the relative density could effectively improve the internal erosion resistance. |
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Assessing Improvement Effect of Sand Compaction Pile in the Ash Pond of Taichung Thermal Power Plant |
黃俊鴻 葉品毅 呂昱達 林茂榮 郭麗雯 |
擠壓砂樁、煤灰、超額孔隙水壓、側向變形、液化、地盤改良 |
本文報告以擠壓砂樁工法改良台中火力電廠灰塘煤灰之成效,探討改良過程中,煤灰地盤所激發之超額孔隙水壓行為與側向地盤變形。改良成效以標準貫入試驗、震測錐貫入試驗以及打樁貫入地層之打擊數來評估。試驗結果顯示,除了地下水位以上較淺層之煤灰層外,擠壓砂樁改良工法對於灰塘具有一定之改良成效。圓錐貫入試驗非常適合用於評估地盤改良成效。 |
This paper presents the ground responses during installing sand compaction pile (SCP) in the ash pond of Taichung Thermal Power Plant. The responses include the excess pore pressure change and lateral ground deformation. Improvement effect of SCP is accurately evaluated by SPT and SCPT investigation methods and blow count number during pile driving through a careful planning and execution. All the results of different methods are highly consistent with each other and the corresponding ground response behavior. The results show that the effect of using SCP to improve coal ash deposit is significant except for the shallow layer above the ground water level owing to its low confining stress. The CPT investigation has the highest resolution to identify the improvement effect and is highly recommended to be used in engineering practice. |
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Ground Improvement of Coastal Soft Soil on Steel Mill |
張志勇 廖惠生 林文焉 黃俊凱 |
軟弱黏土、回填砂土、地盤改良。 |
本文以越南某濱海之鋼廠為例,考量廠址中之軟弱黏土層及疏鬆回填砂土層、建廠施工條件、基地承載力及工後沉陷等地盤改良設計基準,規劃一系列之地盤改良工程。本工程以動力夯實工法(DC)、動力排水壓密工法(DDC)、真空壓密工法(VC)及高真空擊密(HVDM)及其他工法加以組合運用,以達建廠用地之基本需求,文中另提出動力夯實工法及動力排水壓密工法之前導試驗結果,初步驗證地盤改良工法之可行性。目前本工程正全面施工中,本文僅初步闡述地改工法選用之考量原則,提供台灣工程界參考。 |
Many ground improvement techniques, such as dynamic compaction(DC), dynamic drainage consolidation(DDC), vacuum consolidation(VC), high vacuum densification method(HVDM)and other techniques were applied in a steel mill project located within costal area in Vietnam. Soft clay and loose reclaimed sand conditions, construction limitation, target value of allowable bearing capacity and settlements after commercial operation were well considered. Results of the pilot test (DC & DDC) showed well feasibility for further application in this project. The purpose for the article is to provide a helpful reference on selection of ground improvement techniques. |
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Design and Construction of Vacuum Preloading |
吳建閩 江承家 |
軟弱黏土、地盤改良、真空預壓、垂直排水。 |
針對軟弱黏土層之地盤改良,國內傳統之地盤改良施作常以填土預壓工法進行,如國內截彎取直之基隆河廢河道、臺北捷運北投機廠、麥寮六輕等。填土預壓由於需額外大量土方預壓,預壓完成後尚需移除多餘土方。為縮短軟弱黏土層之施工時間及減輕對環境之衝擊,真空預壓工法可作為地盤改良之另一選擇。 本文主要介紹真空預壓之設計與施工方法,說明真空預壓工法應用於地盤改良工程所可能衍生之施工及設計問題,並對真空預壓工法施作程序、監測配置及驗收作一概要闡述,以供未來相關設計及施工之參考。
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The earthfill preloading method is widely used in Taiwan for the project that require soft clay ground treatment such as Keelung river reclamation project, Taipei MRT Beitou Depot and No. 6 Naphtha Cracking Project etc. The technique of improving soil properties by pre-compression consists in surcharge the ground with uniformly distributed surface load prior to the construction of intended structure. To eliminate the needs of earthfill material which is usually expensive and often unavailable and the cost and time of removing the fills, vacuum preload could be used as an alternative treatment method for soft clay. This article describes the design and construction methods of vacuum consolidation. Several issues concerning the practical aspects of the vacuum preloading method are discussed. The construction procedures used for vacuum preloading, the instrumentation and the acceptance of the work are also described.
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Case Study and Analysis of Earth Pressure Induced by Deep Excavation of Finite Soil Body in Sedimentary Soil Deposits |
林宏達 陳建勝 呂芳熾 林永光 黃一昌 林建宏 |
沉積土層、深開挖、有限土體、土壓力、近接施工。 |
都會區進行深開挖工程時,常會遭遇臨近既有建築物存在情況。在既有建築物地下室與新建擋土結構之間存在著有限寬度的土體。國內外若干開挖經驗與土壓力理論研究顯示,此類有限土體於開挖時所引致之側向土壓力較無限土體之土壓力為小。本研究採用極限平衡法探討非凝聚性及凝聚性土壤之深開挖有限土體主動土壓力,並據此推導有限土體土壓力與距牆比(L/H)之關係,且以有限元素法”PLAXIS”程式進行二維數值模擬分析驗證。在工程應用上本研究亦提出一套可將前述有限土體土壓力與距牆比(L/H)關係應用於一維深開挖軟體進行深開挖分析之方法。此方法可合理地將有限土體土壓力效應實際考慮於深開挖分析中。最後,本文擬以實際案例採用上述方法並應用一維程式”RIDO”進行有限土體深開挖分析,並與案例之觀測資料互相比較探討,以進一步驗證本文提出之方法。 |
In an urban region, a deep excavation project commonly involves the existing of adjacent buildings. The limited soil space commonly takes place between the diaphragm wall of the newly constructed structure and the existing structures. Numerous researches and practical experiences have found that the lateral earth pressure under limited space conditions is relatively small compared to that under unlimited space conditions. The limit equilibrium method is adopted to evaluate the earth pressure reduction induced by deep excavation under the limited space conditions of cohesionless and cohesive soils. This study first develops the relationship between the earth pressure and the distance ratio (L/H) relationship. Then, the results of the limit equilibrium analysis are validated with the finite element results using PLAXIS 2D program. Subsequently, the results are incorporated into the 1-D excavation analysis that is commonly used for the practical design. Finally, a case study using the RIDO program is conducted to verify the feasibility of the proposed method. |
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Calibrating the Model Uncertainty of the HBF Simplified Method for Assessing Liquefaction Potential of Soils |
黃俊鴻 陳正興 莊長賢 |
液化、簡易法、可靠度分析、貝氏定理、模式不確定性。 |
本文介紹以土壤液化評估法之可靠度分析與貝氏定理為基礎,利用集集地震與世界其他地震的土壤液化案例,校核世界上常用之土壤液化簡易評估法與作者所發展的雙曲線函數(HBF)簡易評估法之模式不確定性與精確度。各簡易評估法均對集集地震案例有較佳的預測精度與較少的誤差,顯示集集地震案例品質較為良好。各簡易評估法中,以HBF法、Seed(1985)法與NCEER法(1997)有最小的模式不確定性與較小的誤差,明顯優於日本NJRA法(1996)與T&Y法(1983)。HBF法相較於Seed(1985)法與NCEER法(1997),有液化強度曲線公式簡單,參數有明確物理意義等優點,所需要之各種修正公式與係數簡單易記,便於工程實務應用,值得推廣,建議爾後工程界能考慮台灣多年研究所建立之本土性液化評估法。 |
Based on the liquefaction and non-liquefaction cases of the Chi-Chi earthquake and the other world earthquakes, this paper uses the reliability analysis and Bayes’ theorem to calibrate the model uncertainties of the HBF and other commonly used simplified methods for assessing soil liquefaction potential. The results show that all the methods obtain the best predictions for the cases of the Chi-Chi earthquake. Among the methods, the HBF method, the Seed’s method(1985) and the NCEER method(1997) are better than the Japanese methods, the NJRA(1996) and the T-Y(1983) methods, both in model uncertainty and prediction error. As compared to the Seed’s method(1985) and the NCEER method(1997), the cyclic strength curve of the HBF method is simpler and has quite clear physical meaning, and the correction formula needed are also simple and easily kept in mind. Thus, the HBF method is suggested to be used in engineering practice. |
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Study on the Setback Distance and Requirements for Landfill Site Located within the Fault Zone |
黃富國 高思懷 李明國 |
掩埋場、斷層、退縮距離、法規。 |
本文旨在探討斷層對掩埋場之影響及設置法規要求。首先蒐集國內外相關法規及文獻進行研析,並對國內外案例資料進行探討,最後綜合彙整專家會議之結論,提出法規修改的建議。在法規研析方面,國內外建築或土地管理法規顯示,活動斷層附近多列為限制發展區域,或者規定一定的退縮距離;而案例探討結果顯示,活動斷層錯動及其引致的地震,確實對掩埋場設施產生若干程度的影響及損害;本文最後綜合專家會議之意見,活動斷層方面,建議採用衛生掩埋法處理之掩埋場可訂立50至60公尺的退縮距離,而採用封閉掩埋法處理之掩埋場可訂立60至100公尺的退縮距離,若活動斷層位置被掩覆或推定者及存疑性活動斷層,退縮距離加大二分之一,供主管機關修訂相關法規參考,以降低可能風險;非活動斷層方面,則建議逕採工程措施方式,以解決潛在之地質問題及預防可能之污染滲漏。 |
The influence of fault on the sitting of landfill and its requirements are investigated in the study. Both of the internal and external laws, standards, researches and cases were surveyed. The performances of landfills during past earthquakes were also investigated. In addition, expert conferences had been organized to discuss the theme. Finally, some suggestions for amendment of relevant code were proposed in the study. The results of case studies showed that both earthquake-induced surface ruptures and displacements by fault-slip could cause some damages to facilities of landfills. The landfill site around the active fault is usually specified as a restricted development area or stipulated a setback distance in most managed laws of building or land. The specialists of expert conference recommend that it is properly for Taiwan EPA to revise its administrant law. On the aspect of active fault, a setback distance ranging from 50 to 60 meters for sanitary landfill, 60 to 100 meters for security landfill is proposed. One half distances should be added if the location of fault zone is unclear. On the aspect of non-active fault, the engineering measures should be adopted to overcome the potential geological problems and to prevent leakage and pollution of underground waters. |
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Engineering Properties of Soft Ground Condition of Yilan Area |
趙紹錚 黃宏謀 |
宜蘭、軟弱地盤、大地工程分區、液化潛能。 |
宜蘭地區(蘭陽平原)地質多為含有細顆粒含量高的軟弱土壤,加上地下水位面非常接近地表,於交通道路工程及建築結構物興建時,屢遭遇到承載力不足及沉陷量過大的問題。例如國工局進行之北宜高速公路平原段側車道工程,公路總局興建之台9線宜蘭市外環道路,及目前大量建造於蘭陽平原極軟弱土壤上之各類建築物等,隨著結構物量體之增加,軟弱地盤相關工程問題無法避免。由於軟弱地盤可概分為軟弱土壤與易液化土壤兩種特性,本文藉由介紹蘭陽平原地體構造土層厚度、宜蘭縣大地工程分區、蘭陽平原土層整體特性、及土壤液化初步分析等課題,說明宜蘭地區近年來與軟弱地盤工程特性有關之研究成果,提供大地工程界先進規劃設計施工時相關參考資訊。 |
The soft Yilan soils consist of high proportion of fine grained particles with high ground water table conditions. Therefore, bearing capacities and excessive settlements of the road projects and building structures result in many practical problems during construction work. For example, the expressway project of the Yilan Plain section of the Taipei-Yilan express by the Taiwan Area National Expressway Engineering Bureau, the Route 9 Yilan City outer-ring expressway project by the Directorate General of Highways, and those contemporary structures constructed on the extremely soft Yilan soils, all of them have no way to avoid dealing with the inadequate bearing capacities and the excessive settlements problems with the structure’s dimension increasing. Soft ground can be generally classified into two categories, namely soft soil and liquefaction susceptible soil. Thus, this paper presents the recent research results of soft ground condition of Yilan area by means of explaining the subsurface layer structure, the geotechnical engineering zones, the integral soil characteristics, and the liquefaction potential. It is hopeful that the state-of-the-art research findings can be used by geotechnical engineers in planning, designing, and construction phases. |
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