國內河川橋樑施工與汛期影響之研究

Study on the impact of flood season on bridge construction in Taiwan

黃義芳(Yi-Fang Huang)

指導教授 ： 郭斯傑

國立臺灣大學/工學院/土木工程學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.02047

摘要

河川橋施工受汛期影響很大，實際執行與事前評估經常有很大落差，如何對評估做有效改善；又河川橋工程經常受汛期影響，而損失慘重，對施工如何因應，來降低無謂損失。另公共工程發包常受年度預算控制，致發包時程與汛期重疊，對橋樑施工影響遠大。期能透過本研究做為後續公共建設能有更精確評估。
公共工程之工程期限常因「政策目標、建築師、顧問公司之建議及配合相關工程」決定工期。但工期與施工地點所在地降雨量關係至巨，依氣象局96~98年統計資料，宜蘭每年平均降雨198天，台南每年平均降雨85天，相差達兩倍之多，而大多數的作業，除了降雨當時的生產力會降低外，降雨之後所形成的積水、潮濕、工作面或其他條件的改變等，仍然會造成各項目後續的生產力受到影響，有的甚至可能持續數天仍然無法正常工作，但目前所有的降雨評估模式並未考慮到降雨的後續影響。
橋樑主要構件可分成下部結構、上部結構和橋樑附屬工程三大部分。對下部結構而言不論採用何種工法，都會受大雨影響而停工。上部結構部分，如採自動化工法因設備都在完成橋上，只要大雨結束即可恢復施工，所以受影響程度較小。但採就地支撐工法、吊裝工法，大雨後會軟化地盤承載力，臨時支撐受影響大或吊具無法站立相對受影響，將如下部結構，只要大雨來臨前後之一段時間，都受到一定之影響。
橋樑工程之施工進度受汛期影響相當大。然而目前橋樑工程往往配合政策需求，造成發包時程矛盾，咸少用專業判斷，致受雨天影響加劇，因此公共工程經常無法如預期完成，加上低價得標，公務員心態，承包商投機，一切依規定必須公文往返，相對就較難"如期完工"，實現與事前評估相符之目的。本研究在此背景下，以現有的橋樑施工方法，歸納出在汛期間橋樑工程適合之策略及方向。以期縮短規劃與實際狀況之差距。

關鍵字

汛期 ； 工期 ； 橋樑 ； 主要河川 ； 施工風險 ； 營建自動化

並列摘要

The bridge construction over the river was seriously influenced by floods period. Large differences were always found between execution and prior evaluation. It is an important issue about how the efficient improvement can be made onto the prior evaluation. Furthermore, how to decrease the construction risk or possibility loss during floods period is also very important. Since the procurement scheme of infrastructure is governed by annual budget of government, as a results, the procurement schedule and floods period was overlapped and it had a great impact on bridge construction. The goal of this study is to provide accurate evaluate for future infrastructures.
The completion date of infrastructure is mainly determined upon site location, as well as policy, related projects, suggestion of architect or engineering consultant. According to the report issued by Central Weather Bureau, the annual mean of rainy days are 198 and 85 for Yilan and Tainan, respectively, which results in large difference in the amount of working days. Most operations were highly related to the weather and the overall productivity was also influenced by the weather as well. For example, the productivity diminished under rainy days, the operation conditions also changed owing to the slash, wet that caused by rain. However, the present evaluation model seldom takes the impact of rain on productivity into consideration.
The bridge is mainly consists with three components: superstructure, understructure and subsidiary engineering. During the construction of understructure, it was usually broke down for the heavy rain, no matter what kind of construction method was used. On the other hand, as long as automation constructing method was utilized, the construction can be formally proceed after the rain stopped for all the equipments were setting on the bridge deck level. However, when the CIP (Cast in place) or PLM (Precast Launching Method) was utilized for superstructure, the load capacity of ground will be soften by heavy rain and the construction equipment or temporary support system or crane can not standing safety, which was also found in understructure.
The schedule of bridge construction was seriously influenced by flood period. For the construction is usually tie in the policy, which results in schedule delay and usually lack of professional judgement. Combined with bid with unreasonable low price, public official attitude, opportunistic contractor and long-winded official procedures, the construction schedule is hardly efficiently implemented. Based on the conditions and the current methods, this study trying to summarize the appropriate policy and direction that is suitable for bridge construction during flood period and diminish the difference between prior plan and real situations.

並列關鍵字

floods period ； completion date ； major river ； construction risk ； automation constructing

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