自來水管網汰管啟發式篩選程序與優選模式

Abstract

自來水管網會因老舊、腐蝕、劣化、地層運動等因素增加管線損壞機率及降低供水品質，故有必要定期汰換管線以維持供水系統的穩定度，然而由於汰管成本頗高，如何有效率的汰管是一個有必要探討的重要問題，本研究因而依國內案例特性，建立一個程序及應用之前所發展的優選模式於國外案例，以求取在一定成本限制下效益較高的汰管方案。所建議的汰管啟發式篩選程序首先建立數個篩選因子，再依篩選因子排序管線汰換的優先性，之後根據擬汰率上限選取優先擬汰換的管線，並以總供水穩定度評估汰管效益。汰管優選模式是以汰換管線後對管網系統所改善的影響供水量作為權重，並定義汰換管線後之損壞機率改善量為汰管改善效益，據以進行汰管方案優選。 本研究以三區處為案例測試所發展的啟發式篩選程序，根據不同的汰管篩選因子進行排序篩選，均能夠迅速篩選出需優先汰換以及對管網供水穩定性影響大的管線，其中以單位長度供水穩定度因子得到的結果最好。而優選模式則應用在國外加拿大渥太華巿的管網中，以實際的管網案例進行優選模式之規劃求解，且以不同限制成本下評估汰管供水改善效益，在成本2百萬至5千萬加幣間成本限制下所得汰管率約在1.3%至7.1%，供水穩定度約在0.33至2.99 CMD．%間，單位汰管率之供水穩定度以在汰管率1.02%時最高，建議採用汰管率為2.1%時為較佳的汰管方案。

Aging, corrosion, tuberculation, and poor conditions can increase the frequency of pipeline breakages of a water distribution network (WDN) and subsequently reduce its quality of service. Periodical pipeline replacement is thus necessary to maintain the reliability of a WDN. However, the budget for pipeline replacement is generally quite limited. How to replace pipelines efficiently is an essential issue to evaluate. This study developed a heuristic procedure for Hsinchu City WDN and applied an optimization model to Ottawa City WDN for determining effective pipeline replacement plans. The procedure first identifies a set of factors to be assessed. According to the factors, the procedure prioritizes the pipelines for replacement. Then, under the limit of a pre-specified replacement rate, a set of pipelines are selected for replacement. Different replacement plans are compared based on their improved potential water shortage rates. For the optimization model, the objective is to maximize the improvement in the shortage reliability of a WDN after replacement. The proposed procedure was applied to Hsinchu City WDN. With a set of selection factors, pipelines were prioritized and various replacement plans were generated. The replacement plan determined by using the factor of improved potential shortage per unit length is the best one according to segment-based improved potential shortage. The optimization model was applied to a sub-network of Ottawa City WDN in Canada. Under different cost constraints, different replacement plans were obtained using the model. For the plans obtained under the cost constraints between 2 million and 50 million Canada dollars, their replacement rates range from 1.3% to 7.1% and their improved potential shortage rates range from 0.33 to 2.99 CMD-%. The highest improved potential shortage rate per unit replacement rate is the plan with 1.02% replacement rate. And the plan with 2.1% replacement rate is suggested for the studied WDN.