蘭陽溪堤防安全性評估分析研究計畫(2/2)(附光碟)

蘭陽溪水系為宜蘭縣境內最大河川，屬中央管河川；主要支流包括羅東溪及宜蘭河，本計畫範圍為主流右岸之五結(歪仔歪橋下游段)、大洲、中溪洲、中溪洲護岸、紅柴林、三星二號、三星舊堤、三星一號及破布烏堤防，堤防與護岸合計約26,918公尺。因本溪水系現有防洪構造物歷經多年風吹日曬及颱風豪雨後，發現部份堤頂已有下陷、淘空滲砂與材料劣化等現象發生，並歷經民國101年蘇拉颱風、102年天秤颱風、103年麥德姆颱風等沖刷影響之後，堤防受損情況之掌握亟需評估其安全性，期能尋求有效維修與補強工法及研擬改善方案，以做為日後管理與維護之重要參考依據，爰以辦理本委託計畫。 計畫內容主要為河堤檢測及資料蒐集分析建置兩部分，其中河堤檢測部份包括：河堤構造物現場勘查，其範圍為蘭陽溪右岸，共完成3次現場勘查，計有38處損壞，經目視損壞分析評估，計畫改善有34處，注意改善有4處，破壞類型主要為裂縫損壞計28處、其次為坑洞損壞6處。另非破壞性檢測採透地雷達進行堤防孔洞探測，完成測線長度36,211.5公尺，檢測成果堤防輕微孔洞總長度508.5公尺，中度孔洞總長度4.5公尺，無嚴重孔洞訊號；此外透過透地雷達檢測、敲擊回音法檢測、反彈衝錘試驗及鑽心試驗交叉驗證，其驗證成果大多吻合，因此本計畫採用透地雷達進行河堤構造物檢測，其成果可充分掌握河堤構造物內部結構現況。 本計畫採用目視調查成果、非破壞性檢測成果、河堤歷史資料、堤後保全對象、堤身結構評估、環境因素評估及水理分析評估等六項指標作為評估指數，將堤防每100公尺劃分為一段進行評估，結果220段屬正常、46段屬計畫改善、4段屬注意改善，注意改善者為五結堤防7K+940~8K+040、大洲堤防2K+900~3K+000、破布烏堤防1K+300~400及1K+500~600四段，建議應密集注意並寬籌經費修復；而47段屬計畫改善區段，應列為定期檢測及觀測堤段。此外計畫範圍內共計38處損壞，各損壞點位修復評估分析請參閱本報告第六章6-4節所示，維護及修復經費估計約為267萬元。

The Lanyang Creek System is the largest one inside Ilan County administered by the central government; its main tributaries include Luodong Creek and Ilan River. The scope of this project consists of dikes on the right bank of the main branches such as Wujie, Dachou, Inxizhou, Inxizhou Bulkhead, Hungchailin, Sanshing NO.2, Sanshing Old Bulkhead, Sanshing NO.1and Pobuwu in the total length of 26,918 meters. The existing structures of flood wall of the creek system were found partially collapsed, hollowed out, and material deterioration due to long years of weathering effect and struck by typhoon and heavy rains. Especially, after the erosion impact brought by Typhoon Saola in 2012, Typhoon Tembin in 2013, Typhoon Matmo in 2014, serious damages were done and the safety needs to be evaluated. In order to look for effective maintenance and reinforcement initiatives, we conduct this safety evaluation and analysis project and propose the initiative for improvement for the reference of future management and maintenance.
The project consists of two parts: dike inspection and data collection, analysis, and compiling. The former includes: on-site investigation of dike structures to cover the scope of right bank of Lanyang Creek. In three on-site visits, 38 damaged parts were identified. After visual inspection on damages, 34 sites need to be improved by this project and four need to be observed. Damage types are mainly caused by cracks, about 28 sites, followed by six pothole damages. Additionally, the non-destructive testing is conducted on erosion with the ground-penetrating radar to complete the measurement length of 36,211.5 meters. It was found that 508.5m of dike was slightly cleaned out, 4.5m of dike was intermediately cleaned out, and no dike was seriously cleaned out. Furthermore, through the cross-examination of radar testing, impact-echo method, rebound hammer method, and core testing, similar empirical proofs were identified. Thus, this project utilized ground-penetrating radar to inspect dike structures to fully understand the current state of them.
This project adopts six indicators for evaluation: visual inspection result, non-destructive testing result, historical information of dikes, dikes preserved, evaluation of dike structures, environmental factors, and hydraulic analysis evaluation. Every 100-meter dike was marked as one section for evaluation; 220 sections were found normal while 46 were required to be improved by the project, and four need to be observed where are located at four sections of Wujie Dike 7K+940~8K+040, Dachou Dike 2K+900~3K+000, Pobuwu Dike 1K+300~400 and 1K+500~600. We suggest that intense monitoring is required and the budget shall be allocated for repairing. The 46 sections that need to be improved by the project shall be listed for regular inspection and monitoring. Additionally, for the total of 38 damage sites, please refer to Chapter 6-4 for repairing evaluation and analysis. The amount for maintenance and repairing totals 2.67 million.