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| ON ANALYSIS AND ASSESSMENT OF NEGATIVE SKIN FRICTION OF CAST-IN-PLACE BORED PILES |
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| 陳斗生、楊恆偉 |
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| 負摩擦力、超載、質流、大規模回填、樁載重試驗、t-z曲線 |
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| 在基礎工程實務中，由於土層之擾動，回填等超載，或地下水超抽皆可能使樁基礎受到額外之負摩擦力而產生負面效應。但負摩擦力之量化及其變化之預估尚未有一致而相對簡易之評估方法。本文提出之負摩擦力評估法及評估步驟係根據其產生機制，以質流理論說明其變化，並援引大規模回填案例實測之負摩擦力變化數據；然後採用樁載重試驗結果及所獲之t-z曲線，以電腦模擬分析模式，估算基樁受到進一步載荷下產生位移時負摩擦力之消長及預估基樁在各載荷下之荷重傳遞分佈曲線；並由此分析結果檢討評估基樁在各受力階段之安全性。 |
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| In this article, a method and procedure is proposed based on the observed significant negative side skin friction occurred to pile foundations, employed the concept of creep and relaxation and through a series of study which consisted of monitoring of settlements of various soil stratum and the induced pore water pressure during pile installation, instrumented full scale pile load test, and artificial surcharge test fill. By using the data collected, an analytical model using t-z curves may be used to evaluate the variation of negative skin friction and the future behavior of the pile foundations under additional loads |
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| MONITORING AND ANALYSIS ON SOIL STRATUM DISTURBANCE INDUCED BY REVERSE-CIRCULATION AND ALL-CASING PILING |
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| 何樹根、楊恆偉、高大洲 |
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| 地層擾動、地層流失 |
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| 近期在台灣都會區以外之重大交通工程建設大都採高架之施工方式，而在雲、嘉、南平原區域因地層之承載力不足，高架橋之基礎因而大量採用樁基礎。在台灣基樁之工法雖已相當多樣化，但在平原、高地下水位之地區主要仍採用全套管樁或反循環樁；由於工程建設持續推動過程中，橋梁互相跨越或接近已無法避免，因而在既有基樁近距離內施作基樁之機會大增，新作基樁對於地層之擾動是否足以對既有基樁造成影響成為一個課題。本文介紹位於嘉義地區之實尺寸試驗，以CPT包括實際於基樁施工過程量測地層之變化行為，並評估前述兩種基樁施工法對於地層之擾動性，量測基樁施工前後地層之性質變化、基樁鑽掘引致之孔隙水壓變化、地層側向變位及垂直沉陷。綜合各項量測成果評估在試驗所在之地層，全套管工法有異於一般工程上之認知，其施工對地層之擾動明顯大於反循環工法，其主要原因推估為全套管工法鑽掘時易造成砂土地層流失。 |
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| Viaducts are commonly used in the transportation engineering in non-urban area in Taiwan recently. Because of poor underground condition, pile foundations are required for most viaducts in the Yunlin-Chiayi alluvial plain. Although piling methods are diversified in Taiwan, two piling methods, Reverse-circulation and All-casing, are most frequently used in plain area. For new viaducts constructed in the vicinity of existing viaducts, the possible adverse effects of adjacent piling on the existing foundation becomes an engineering subject to examine. This paper introduces tests conducted to evaluate the influence of piling on the adjacent underground strata at Taipo Chiayi. The tests included the monitoring of underground response when two different piling methods, an all casing and a reverse circulation , were used. According to the monitoring results, there are evidences to show that piling will disturb the adjacent underground soil strata. Such disturbance may influence the existing adjacent structures. The All-casing method had a greater disturbance on sandy soils because sandy soils may flow into the drilling casing and result in ground settlement and lateral displacement. |
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| USING LOAD TESTING RESULTS TO EVALUATE THE LOAD TRANSFER CHARACTERISTICS OF BASE-GROUTED BORED PILES |
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| 張有恒、葉仁德、謝旭昇、王崑瑞 |
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| 樁底灌漿、先期試樁、鋼筋應力計 |
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| 鑽掘基樁經過良好的樁底灌漿程序之後，如果直接由樁頂荷重與沉陷量之曲線關係研判，均可証明樁整體之容許承載力明顯提高。但樁底灌漿可能改變樁周摩擦應力及樁尖點承應力之分佈比值，因此應用樁底灌漿於先期試樁時，應謹慎評估樁周摩擦應力及樁尖點承應力之量測資料。本文列舉了台灣三處大型工地先期試樁及一處工地樁底灌漿時進行同步監測之結果，經由解析樁身所埋設之鋼筋應力計量測數據，可了解樁底灌漿對樁身軸力分佈、各地層摩擦應力與樁尖點承應力之影響。 |
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| Various published papers and pile load testing results had shown that base-grouting the pile tip can significantly improve the allowable bearing capacity of bored piles. However, base-grouting may change the ratio between skin friction and end bearing. Therefore care must be taken to correctly interpret the load test results of a base-grouted pile. This paper describes pile load testing results of several sites where instrumented bored piles had been base-grouted and tested. The effects of base-grouting on the distribution of axial force, skin friction and end bearing were evaluated based on measurements of rebar stress transducers. |
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| CASE STUDY OF DESIGN AND CONSTRUCTION OF LARGE DIAMETER BORED PILES AND WELL FOUNDATION |
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| 黃崇仁、林義評、王志賢、羅立、李友恒、高耀宏 |
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| 大口徑基樁、全套管基樁、井式基礎、樁載重試驗 |
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| 因應大跨度跨河構造物及921集集大地震後對近斷層效應之認知，造成橋梁基礎承載力要求極大，須採用較以往更深且更大口徑之基礎。本文以工程案例說明橋樑基礎型式的選擇原則與優劣比較，並藉由樁基礎與井式基礎的設計與施工過程，配合樁載重試驗結果，探討因應工程地質特性的設計方法及施工所衍生的相關問題與對策。 |
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| To accommodate the construction of long span bridges and to resist severe near-fault seismic forces, deeper and larger foundations capable of providing extremely large bearing capacities are often adopted in modern day bridge foundation design. This paper provides case histories to illustrate the advantages and disadvantages of selecting between large size pile foundation and caisson foundation. Design and construction procedures together with pile load test results of these high capacity foundations are addressed. Problems/solutions associated with the design/construction of these high capacity bridge foundations are discussed as well. |
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| CASE STUDY OF THE CONSTRUCTION DIFFICULTY OF A LARGE-DIAMETER FULL-CASING PILE PROJECT |
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| 王淳讙、林宏達、徐力平 |
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| 全套管基樁、束管、承載力、SPT-N值 |
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| 為了抒解台北都會區之交通量，並且兼顧使用者之行車安全性，東西向快速道路位於八里新店線段之基礎設計大量採用全套管基樁。因為用地限制及載重之需求，樁基礎多為大口徑之長樁。此一特性造成施工之困難度增加，而發生工程困難之風險亦同時增加。本文說明八里新店線A標段內工程於施工時所遭遇之基樁束管現象，尤其著重於樁號NO.1R及NO.2L於施作時發生束管之原因探討，包含探討此區域之地質特性、全套管基樁施工特殊需求、基樁承載力設計相關規定等。而後根據討論結果，提出此區域之基樁承載設計相關建議。 |
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| In order to alleviate the traffic congestion problem among the Taipei metropolitan areas, the Bali-Shinden line of East-West Expressway System project is designed to satisfy both the traffic volume and also the safety of driving during the rush hour traffic. This project is designed with the long and large-diameter pile, which increases the risk of occurrence of construction difficulty. The construction difficulties occurred during the casings installation of pier numbers of NO.1R and NO.2L, in which cases, casing were restrained by the surrounding soil and thus stopped the machine from further driving and withdrawing the casing. This paper summarizes the event of this construction difficulty and investigates its causes by reviewing the local geology and pile design process. The discussion at the end of paper provides possible causes of the restrained casing situation and suggests possible revisions for future pile design. |
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| RELATIONSHIP BETWEEN INFLOW (LEAKAGE) OF HSUEHSHAN TUNNEL AND CONSTRUCTION、HYDROLOGICAL ENVIRONMENT AND OPERATION MANAGEMENT |
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| 張文城、張龍均、黃鳳岡 |
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| 地下水、湧水、抽坍、滲水 |
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雪山隧道為北宜高速公路隧道群中最長的一座隧道，全長12.94公里，雪山隧道位於雪山山脈，穿過經輕度變質之沈積岩層，由於岩層受板塊衝擊影響，造成隧道沿線地質構造複雜，變化劇烈，又藴藏豐沛地下水，致施工期間導坑及兩條主隧道曾發生多次湧水抽坍或受困。
雪山隧道依規劃設計期間之調查，隧道全線均位於地下水位之下，為消解儲於岩盤內地下水壓之影響，隧道設計為排水隧道，並於施工階段對雪山隧道湧水問題進行鄰近地區水文調查評估工作及建立隧道開挖施工遭遇地質弱帶湧水抽坍處理機制。此外雪山隧道結構複雜且斷面變化頻繁，致出現整體防水層的功效未臻完善之微量滲水事件，亦已建立因應改善措施處理機制。本文擬就前述經驗與案例深入檢討，期能提供工程界爾後類似案例研討的思維方向。
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Hsuehshan Tunnel, 12.94 kilometers long, is the longest tunnel of Taipei-Yilan Expressway. Hsuehshan Tunnel is located within the Hsuehshan Range sub-province, which is composed of slightly metamorphosed sedimentary rocks. The rocks have been folded, deformed and sheared by tectonic activities. Locally large quantity of groundwater inflow and cave-ins were encountered due to very high permeability of the rocks and high groundwater table during tunnel excavation.
Hsuehshan Tunnel deeply below the groundwater table is designed as a drainage tunnel. The inflow to the hydrological influence of the neighboring areas was studied, and treatments of cave-ins owing to large quantity of inflow in geological weak zones were established during tunnel excavation. Slight leakage occurred due to the bad working condition and structural complexities of the intersections. The leakage treatments have been established after completion of tunnel lining.
The experiences of treatments of cave-ins and leakage are described in delail as references for similar engineering encounters in future.
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| HYDROGEOLOGICAL INVESTIGATION AND ANALYSIS OF TRANSBASIN DIVERSION TUNNEL OF TSENGWEN RESERVOIR |
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| 楊豐榮、顧承宇、譚志豪、許世孟、鍾明劍 |
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| 隧道工程、水文地質調查、隧道湧水、地下水、三維數值分析 |
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| 台灣地區因雨量充沛，且位於歐亞板塊與菲律賓板塊交接處，活躍的造山運動造成岩層之破碎度高而節理發達，故地表水易沿地質弱面滲入岩層，以致岩盤中之地下水儲量豐富。近年來山岳隧道之開挖經驗顯示，穿過高山地形之長隧道因水文地質條件十分複雜，隧道施工時除因大量湧水造成施工困難外，亦常因地下水流失引發鄰近區域環境水文地質之爭議。本文以曾文越引隧道工程為例，分別針對：(1) 山岳隧道工程之水文地質現地試驗技術、(2) 結合地形、地層、地質構造及地下水文條件之水文地質概念模型建立、(3) 區域三維水文地質數值模式之分析、(4) 模式率定與驗證、與(5) 隧道開挖湧水對鄰近區域水文地質環境影響之分析等項目詳加探討。並期藉此降低隧道於施工時所可能遭遇之風險，以釐清隧道施工與營運對於周遭環境水文地質之可能影響。 |
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| Taiwan is located at an active mountain belt created by the oblique collision between the northern Luzon arc and the Asian continental margin in which fissures, joints, beddings, and even faults prevail in most of mountainous areas. While existing joints and fractures provide ideal conduits for water to flow, large volumes of groundwater are stored in aquifers in which water inflows are often encountered during tunneling. Recently, several case studies of tunneling in Taiwan demonstrate that the water inflow is the major cause for the failure. As a consequence of groundwater loss, the problem of environmental arguments may also arise. In this paper, a case study of Tsengwen reservoir transbasin diversion tunnel with emphasis on the topics of hydrogeology was presented. Several major issues, including (1) the hydrogeological field testing technique, (2) the establishment of conceptual model, (3) the modeling of three-dimensional groundwater flow, (4) the calibration and verification of the conceptual model, (5) the prediction of tunnel inflow, were introduced. The application of each approach was described in details. It is believed that the predicted results may provide useful information for reducing the uncertainties of tunnel inflow and may also clarify the impact of environment issues. |
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