圖書典藏及影音數位平台

花蓮溪原名紅巖溪，流域位於台灣東部花蓮縣內，北接吉安溪，南界秀姑巒溪流域。本溪幹流全長57.28公里，流域面積1,507.09平方公里，主要支流有五條均在西側，由南往北依序為光復溪、馬鞍溪、萬里溪、壽豐溪及木瓜溪。 本溪支流坡陡流急，崩山處處，每遇颱洪挾帶巨量砂石而下，數小時內即由橫谷進入縱谷平原。河床比降在谷口由急陡驟變為百分之一左右坡度，使砂礫淤積於下淤平原段，威脅溪旁兩岸人民生命財產安全，故防洪構造物之安全性影響甚大。 花蓮溪堤防多屬老舊堤防，為能尋求有效維修與補強方案，擬藉由安全性評估計畫來全面檢視花蓮溪堤防之安全，以利後續維護管理。 本計畫主要目的為暸解花蓮溪堤防內容結構現況，採用非破壞檢測方式，檢查堤防構造物之使用狀況與內部損壞狀態，包含結構體內部裂縫及含水狀況等情形，以便未來做為堤防管理、維護之參考依據，以及尋求有效維修與補強方案，擬委外辦理安全性評估分析及研擬改善方案。

The levees along Hualien River were built a long time ago plus the flood-control structure underwent years of exposure to the wind, sun, rain, invasion from typhoon torrential rains, and earthquake. Consequently some of the levee sections showed top of levee sinking, hollowing-up, leakage, and material aging and deterioration, well as other conditions. To seek for effective maintenance and reinforcement solutions in order to assure the safety of the life and property of people on along the river, it is necessary to execute the safety test evaluation project which will carry out the overall inspection of the level safety of the river systems in Hualien, thereby attaining subsequent maintenance and management. 1. Scope of Project and Major Work Items The scope of this project includes the levee and revetment of Lao River, North Cingshuei River, Fenglin River, South Cingshuei River, and Guangfu River. The content of project work is divided into: (1) Facility site inspection of levee structure. (2) The investigation of levee structure strength adopted drilling core sample to conduct compression test with incorporation of rebound hammer test for the comparison and verification. (3) Non-destructive inspection, adopting the execution of ground penetrating radar to detect cavities in levees. (4) Data collection and analysis, and levee safety test evaluation,with drafting for recommended maintenance and repair solutions and the direction of subsequent maintenance and management. 2.Basic Data Investigation for Scope of Project 1.Capability for Water Conveyance (1.)Lao River: The capability of water conveyance from the confluence to Lao River Bridge section passes peak discharge for the 50-year recurrence interval of protection standards. (2.)North Cingshuei River: Except for the slightly inadequate height in existing earth due to the absence of levee establishment on the right bank of cross-section 1 of the exit, the rest can satisfy the peak discharge for the 50-year recurrence interval of protection standards. (3.)Fenglin River: Except for the slightly inadequate height in existing earth due to the absence of levee establishment on the right bank of cross-section 1 of the exit, the rest cross-sections can satisfy the peak discharge for the 50-year recurrence interval of protection standards. (4.)South Cingshuei River: The existing capability of flood relief can pass the peak discharge for the 50-year recurrence interval of protection standards. (5.) Guangfu River: Due to the more serious siltation with Daxing Bridge, cross-section 60 could not pass the peak discharge for the 100-year recurrence interval of protection standards while the rest sections of river levees can pass the peak discharge for the 100-year recurrence interval of protection standards. 2.Investigation of change in the flow route of channel (1.)Lao River: The change of channel at the upstream river section was small while the change of channel at the levees of midstream and downstream sections. (2.)North Cingshuei River: The current flow route was inclined to develop leftward at the turning point of channel between cross-section 9 and cross-section 13 due to Typhoon Morakot. The flow routes under cross-section 8 swings left and right with at low level. Channels over cross-section 13 showed relatively smaller change due to the channel limitation of geology and existing flood prevention facilities. (3.)Fenglin River: According to the 1996 alignment plan, the west side of Western Line was built with a bypass channel connecting to the original channel, and thereby the flow routes between cross-section 13 and cross-section 16 are divided into two. The rest channels showed smaller level of change. (4.)South Cingshuei River: In 1999, Jingfong Bridge was built with levees while the entire channel was also diminished to about 80-100 meters. (5.)Guangfu River: The the level of change before 2000 was considerably larger but the change of flow route became relatively lower due to the limitation of existing flood prevention facilities. 3. Facility Site Inspection Results of Levee Structure 1. Processing Conditions The scope of the regular inspection for this project includes 43 levees with a total length of 43.583m, which has been completed between February 12 and February 14, 2018. The comparison of on-site investigation measurement and review of flood prevention record shows that 9 sections of actual levee lengths do not match with those indicated in the content of contract. 2.Inspection Outcome There were 43 sections of levees with total length of 43,583m. This regular inspection of the levee structure facilities revealed 15 damages while the majority of damage type consisting of cracks and damage on the shallow surface. Additionally Dazhong No. 3 revealed small cavity damages and was hence included in project improvement. Multiple vertical cracks were discovered on the top of Fuguo Left-bank levee, in length of 320m and width 0.3~5cm, and hence were included in attention for improvement. 3.Secondary Review Status The 9th River Management Office has completed the repair of damage in Dazhong No. 3 Levee and Fuguo Left-Bank Levee through the open contract this year. Additionally, the River Management Office conducted regular inspection outcome for the levee structure with the management units and process the secondary review on May 9, 2018. In consideration of the scale of damage without impact on the levee structure, hence the 13 damages were temporarily unrequired for the improvement plan but only listed for follow-up monitoring. 4. Inspection Result of Non-destructive Inspection The project adopted non-destructive inspection method including ground penetrating radar for detection, rebound hammer test, and drilling core test. The test results underwent cross-examination and comparison with the results mostly conforms to reality. The results can be fully applied to control the status of the structure inside level structure, as described in the following results: 1. Ground penetration radar detection results The quantity indicated in the contract – 34,800 meters, was completed for the test line length of 35,390.5 meter. The test results were analyzed and revealed that signals of shallow voids are signals of minor level in shallow voids with a total of 594m, accounting for 1.68% of total test line. The signals of shallow voids form sporadic distribution with the majority of excellent levee conditions. Nonetheless the test line detection at Fuguo Right-bank levee revealed 11m signals of minor shallow voids out of 116m while the detection of Fuguo Left-bank levee revealed 74m signals of minor shallow voids out of 1,158m, which has a relatively higher percentage in cavity accumulation. 2. Investigation of levee structure strength The investigation method adopts compression resistance in drilling core test incorporated with rebound hammer test for verification. A total of 18 areas underwent strength investigation, which strength of compression resistance falls between 152kgf/cm2 and 585 kgf/cm2. The drilling core compression resistance data show that currently the strength of levee material is still in excellent condition without apparent aging and deterioration. On contrary, the rebound hammer test were conducted in 18 test points with rebound values distributed between 21 and 40 (refer to Table 4-63). The average value of the test areas is 28.61 while variance coefficient falls near 18.43%. In spite of the positive correlation between the average values of compression resistance strength of drilling core tests and rebound hammer test, the formula related coefficient regressed was not high enough, which reason could be related to the partial surface aging and deterioration on the surface concrete of the levee. 5. Levee Safety Test Evaluation Results The 21 sections of levee and 2 sections of revetment within the scope of this project underwent safety test evaluation by section of every 500 meters, dividing into 103 sections. The evaluation results showed that 81 sections were normal and 22 sections were included in the plan improvement without attention for improvement and sections of immediate improvement. 6.Subsequent Treatment for Levee Section Damage in Scope of Project There are still 13 cracks and surface AC damage in the scope of this project, which level of damage is classified as follow-up improvement. According to the repair techniques suggested and the actual length, width, depth, and damage type as well as other conditions of each damage point, the amount of materials needed and labor costs were estimated. The total improvement fund needed sums up to approximately NTD351,000. Keywords: Hualien River, Non-Destructive Inspection, Safety Test Evaluation