管齢及び浸入水量の調査結果に基づく下水道管渠の残存耐用年数の統計的推定

摘要

浸入水量の調査結果は，アセットマネジメント的には，すなわち残存耐用年数の推定には利用されていない．しかし，水密性は下水道管渠の最重要の性能である．その評価のため，マクロ的には処理場流入水量から有収水量を差し引いて不明水量を算出する方法並びにミクロ的にはマンホールスパン単位でテレビカメラ調査及び水密性試験が行われている． そこで本研究は，国総研公表データ及び下水道統計データを解析し，個別管渠について，管齢及びテレビカメラ調査結果又は水密性試験の浸入水量測定結果から残存耐用年数を統計的に推定する手法を提案する．%Using the Weibull Curve as the research result of Kazuya FUJIU and Chizato Miyauchi (2007) and the 65535 TV camera investigation data collected and published by National Institute for Land and Infrastructure Management (NILIM 2011) of Japan Government, three Weibull curves are newly calculated as shown in Fig.-2. These four Weibull curves separate graph area into five segments of deterioration levels as shown in Fig.-6. Based on the figure, if the sewer age and the TV camera investigation result, namely the Infiltration/Inflow (I/I) condition such as level-a, b or c are obtained, the very sewer deterioration curve and the remaining service life years can be predicted as shown in Fig.-8. Using the 881 non revenue sewerage ratio data of the sewerage statistics edited by Japan Sewage Works Association, three regression lines for the 137 combined sewer system data, the 744 separated sewer system data and whole 881 data are calculated as shown in Fig.-4. These lines are confirmed to pass inside the 6 data plots of published I/I investigation papers as shown in Fig.-7. Using the applicable line in the figure, if the sewer I/I investigation result, namely the sewer I/I rate is obtained, the remaining service life years can be predicted as shown in Fig.-9.