污水下水道是現代文明之象徵，污水下水道建設為都市健全發展之重要公共設施，亦是都市文化及生活品質進步的指標。污水下水道於建設初期主要投資於收集系統之主、次幹管及處理系統之設施上，未來台灣地區污水下水道分管網工程之推行遂成為建設之重點。 污水下水道分管網工程之施工皆為地面下作業，其所面臨之施工階段風險因素更是以地下未知情況居多，這些風險因素造成之影響主要可歸納成「進度」及「成本」兩大層面。因此考量風險因素對進度及成本造成之影響將是相關工務機關於編列施工預算及工期時之重要課題。 本研究希望探求污水下水道分管網施工時可能遭遇的各種地下不確定性因素並建構適合之風險量化評估模式以對各種不確定性因素進行量化分析，希望風險量化之評估結果可做為相關機關編列施工預算及制定施工工期之調整依據。 本研究經系統性歸納整理後，將地下不確定性因素分成三大影響層面及十二項層面因子，並透過本研究建立之量化評估模式，以專家問卷之方式調查工程主辦單位、工程顧問公司及專業營造廠商等對於風險因素之發生機率及衝擊影響損失之評估，並據此進行風險值之計算，希望風險量化之評估結果可做為相關機關編列施工預算及制定施工工期之參考，其做法為將各種影響因素對預算及工期造成之間接影響，反應到實際執行之預算及工期上，使實際之預算及工期趨於合理化。 The impediment of sewerage pipe construction lies in urbanization. The higher the needs of construction, the greater construction risks there exist underground. This instantly leads to the need to closely investigate the nature of underground risks in sewerage pipe construction. Regardless the source of risks to underground pipe construction, the outcome will be both cost-oriented and schedule-oriented. The characteristics of the source of risk, or uncertainties, form the base to assess the probability of a particular risk. In terms of risk management, therefore, to understand the risk is to evaluate the probability of a given uncertainty and the loss (cost and schedule outcome) resulted from the risk. Understanding of these risks will enable project management to better plan construction by devising a realistic budget and schedule. This work takes a direct approach to assess such risks. Interviews and questionnaire surveys are performed with domain experts. The questions concerning underground construction risks are classified into three aspects, encompassing twelve factors. The survey results are transformed into quantitative forms for later computation and interpretation. A simple methodology is also proposed, as to how the risk assessments can be associated with budgeting and schedule planning.
