圖書典藏及影音數位平台

秀姑巒溪流域位於台灣東部，地跨花蓮、台東兩縣。其北接花蓮溪流域，南與卑南溪流域相鄰，主流秀姑巒溪發源於中央山脈崙天山南麓，東流入台東縱谷後，受海岸山脈阻擋，乃沿縱谷平原向北流，在匯納兩岸諸水後，於瑞穗鄉舞鶴山前再折轉向東流，並以其巨大侵蝕力橫切海岸山脈，而在豐濱鄉大港口附近流入太平洋。流域行政區域包括台東縣之海端、池上與花蓮縣之富里、卓溪、玉里、瑞穗、萬榮及豐濱等八鄉鎮。本溪流域為台東縱谷平原三大水系之一，流域面積1,790.46平方公里，其在花蓮縣部份，占全縣面積三分之一強，居住人口約十萬人，占縣人口三分之一弱，主流全長81.15公里，為全台21條中央管河川之一。主要支流有五條由南至北依序為：樂樂溪、卓溪、豐坪溪、紅葉溪及富源溪。 秀姑巒溪現況防洪構造物多屬老舊堤防，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秀姑巒溪堤防之安全，以利後續維護管理。 本計畫主要目的為暸解秀姑巒溪堤防結構現況，先以人員目視進行檢查並提出期初報告，後續採用非破壞檢測方式如透地雷達探測、震波測勘等，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淘空狀況等情形，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。

1. Project Cause and Benefit The current flood proof structure of Xiuguluan River built a long time ago. The potential risk caused by the climate change, extreme rainfall incident and flow route changes in recent years is considered. In order to understand the current structure situation of Xiuguluan River, the visual inspection of levee surface is carried on by personnel first. Then, the non-destructive ways, such as ground penetrating radar, seismic way, are adopted to inspect the use condition and internal damage status of levee structure, so that the results can be used as the reference basis for future levee management and maintenance. The safety assessment and analysis as well as the improvement measures will be handled to seek for effective maintenance and reinforcement alternatives. In this project, three times of visual inspection were conducted for 49 levees in 46,027m total: As for the non-destructive inspection, 34,800m was inspected by the ground penetrating radar, and 500m was inspected by the seismic wave; 18 places of river levee were investigated for structural strength, the drilling core test was used mainly, and the cross inspection results of resilient hammer test and impact echo method were used for verification. The safety assessment for current situation of levee was conducted by integrating various inspection outcomes, and the improvement countermeasures were drafted in accordance with the assessment result. The main project benefits are: (1) Field investigated the damage situation for external structure of river levee for assessing and grading, listed the dangerous levee section of river and proposed the preferable improvement alternative. (2) Employed the non-destructive testing to understand the current levee internal structure situation and whole damaged condition, proposed the levee safety assessment and analysis and drafted the renovation countermeasure. (3) Proposed the optimum alternative of maintenance management, and the recommendation for the improvement of the existing flood proof structure. 2. Basic Data Investigation for Scope of Project 秀姑巒溪上游段(含鱉溪、九岸溪)水利建造物安全性檢測計畫 vi The scope of this project is the upstream of Xiuguluan River. Among them, the design flowrate Q100 before the merge of Xiuguluan River and Lolo River is 3,720cms, and the slope lowers about 0.64~2.61%, which is class D pigtail flow route; The design flowrate Q50 of Bai River is 457cms, and the slope lowers about 0.55~1.54%, which is class G zigzag flow route; The design flowrate Q50 of Jouan River is 238cms, and the slope lowers about 2.19~3.88%, which is class G zigzag flow route. As for the hydrological analysis results of 2016 “Review on Governance Planning of Xiuguluan River”, except the design at right bank of Xiuguluan River cross-section 26 is open levee for discharge of inner water, it is not satisfy the planned flooding water level. There is no levee between tributary Bai River cross-section 02 to 02-1 at left bank of Bai Bridge, the flood may overflow to high beach farmland. In addition, the cross-section 01 right bank is the Fuli Levee of Xiuguluan River, the height of levee is not reaching the elevation of main stream cross-section 75-1, the flood may overflow, and other river sections can meet the planned flowrate. In the project area, except early newly-built levee sections, the damage and maintenance record of other levee sections is scarce. The protection block or spur dike is laid along the levee, so the protection ability for beach land is sufficient. Only a few levee sections have the approaching flow route, and except that a few cross-section foundation depth is still deeper than the deep trough of flow route, other projected levee foundations are higher than the deep trough of flow route. So, according to Lacey (1930) partial flushing equation, estimate that under the planned flowrate, the possible distance of lateral flushing to the embankment, and involve the beach width and levee foundation depth to assess if the protection ability of beach is enough. As for the analysis results, the protection ability of 25 beaches at left and right banks is slightly poor in the project area. There are 17 historical natural earthquake disasters in the project area. There is highly dangerous landslides potential river at the upstream of Jouan River basin. The flooding positions locate at river terrace at both sides of Xiuguluan River 秀姑巒溪上游段(含鱉溪、九岸溪)水利建造物安全性檢測計畫 vii water system and adjacent villages, such as Dafu Village and Dafong Village of Kwangfu Township, Kangko Village and Jeinpu Village of Fongbin Township, Juisui Village and Hoekang Village of Juisui Township, Sanming Li and Kwangyin Li of Yuli Town. 3. Visual Inspection Results of Levee The visual inspection work of this project was conducted on February 11~13, 2018. There were 15 damaged places found by the inspection, in which 9 places at Xiuguluan River. Most damages were the crack on top of levee, and a few damages were damage and peeling of slope surface. There were 6 places at Bai River. Most damages were the crack on top of levee, and a few damages were cavity, fracture or sink and misplace etc. There was no significant damage at Jouan River. In addition, the other 9 abnormal places with slightly damage which will not endanger the safety of flood proof structure, they will be observed continuously, and will be inspected irregularly at flood season or subsequent casual inspection. The recheck of regular inspection was handled on May 9, 2018, wherein 2 damaged places had been repaired in 15 damaged places. The damaged place of Fuli No. 10 Levee was not within the scope of project. The other 10 damaged places at Shiping No. 7 Levee, Shimin Levee, Fuli No. 7 Levee would not affect the flood proof safety, which were listed for continuous observation. So, the inspect result was adjusted to 2 places should be planned for improvement, and 19 places should be observed continuously. Among them, the foundation damage at Liensui Levee 0K+538 and the crack at Leunten Levee 2K+779 should be planned for improvement, and the damage had already been improved before October 30. Other 19 abnormal places should be observed continuously. Because there is no immediate danger, they did not have the emergency of repair. At current stage, during the flooding period, the major patrol, observation for the trend of severe change at damaged places should be used to grasp the current levee situation in the project area. In addition, upon considering that part of river sections within the range of project belong to class D pigtail flow route, so adopting the unmanned aerial 秀姑巒溪上游段(含鱉溪、九岸溪)水利建造物安全性檢測計畫 viii vehicle to take the high altitude photographs, and recording the direction of flow route and the situation of embankment beach. On February 12, 2018, taking the photographs of Bai River confluence place and Minsing No. 1 Levee sections. On May 10, taking the photographs of upstream and downstream sections of Lungtien Bridge and Dongchu Levee sections. Because there are several tributaries merging into both sides of river, and the river has already entered the range of East Rift Valley, the width of river is increased gradually, so that the flow route is migrated in disorder indefinitely. Among them, the upstream of Lungtien Bridge is the confluence place of Jouan River and Lungtien River, which is influenced by the merge of tributaries at both banks, so the water flow is swung to both banks indefinitely, and several flow routes are closing to the embankment. 4. Inspection Results of Non-destructive Testing In this project, the ground penetrating radar was adopted to detect the levee in 35,843m of length. Because the 0206 Hualien Earthquakes was occurred during the execution period of project, in order to inspect the situation at the bottom of flood proof structure, the contract was changed by the authority and approved by the EPA. The 3,607.5m of ground penetrating radar testing was moved to the Beibing Levee, Huajen Levee, Dongchang Section 1 Levee, Dongchang Section 2 Levee, and Kuoshing Revetment. In this project, the testing was adopted to detect the levee in 35,843m of length. It was found that 317m of levee had slightly cavity signal, and 7.5m of levee had intermediate cavity signal, which accounted for 0.88% and 0.02% of total measurement length, respectively. The intermediate cavity signal located at 2K+112 and 2K+116 of Funan Levee Section 2 of Xiuguluan River. In addition, There were more slightly cavity signal in proportion at Loshan No. 4 Levee and Chutien No. 2 Levee, which shared between 5.93~9.25%. Take a broad view of levee inspection results of this project, parts of cavity signal located at adjacent crack of levee, inferring that the cavity must be caused by the penetrating crack in the area. The penetrating crack makes the levee structure possessing weak surface, and apt to cause the waterway, and then because 秀姑巒溪上游段(含鱉溪、九岸溪)水利建造物安全性檢測計畫 ix after the exterior water is permeated through the levee within the body, taking away some basal soil progressively. Finally, the soil sinks to produce flushing phenomenon within the levee body. Some flushing areas also locate near the construction joint (expansion joint), the function mechanism is also the same. As for the strength of levee body material, the compression strength of drilling core samples was 106 kgf/cm2~377 kgf/cm2. The strength of concrete material was lower at Liensui Levee 0K+750. The compression strength of other drilling core samples was above 180 kgf/cm2 in level. The strength of resilient hammer test was between 146 kgf/cm2~ 404 kgf/cm2. The strength data of field drilling core testing samples and the original resilient data were used to create the correlation curve. The correlation relationship of curve was not high. The reason might be that the resilient hammer test is used to inspect the hardness of material surface instead of strength. It is apt to be influenced by local aging or degradation of concrete surface or the supporting force behind the concrete. The estimated strength is not as reliable as the value of drilling core test. Only relative strength of concrete can be obtained. But the inspection belongs to non-destructive testing, and the operation is convenient and quick, which is suitable for testing in a large amount. 5. Current Condition Assessment Results of Levee After marking the visually inspected damage positions on the ground penetrating radar drawing, the cross verification and comparison of inspection results could be conducted. The results showed that most damage points of levee were the damages without penetrating through the slope surface. According to the abovementioned test data, and refer to “Technical Directions for Hydraulic Structures Inspection and Safety Evaluation”, “Methods for Hydraulic Structures Inspection and Safety Evaluation” of Water Resources Agency, “Administrative Methods for Maintaining River Bank and Coast Security facilities” of Japanese Port and Harbor Technical research Institute, and “Life Cycle Evaluation System of Hydraulic Structures” of US Army Corps of Engineers, to establish a set of current condition assessment system of levee. 秀姑巒溪上游段(含鱉溪、九岸溪)水利建造物安全性檢測計畫 x The assessment results showed that the condition of most levees was very good. The scores lie between 11 points and 34.2 points in every levee, in which 18 sets should be planned for improvement and 111 sets of levee sections are all normal grade. The sections planned for improvement were caused by insufficient protection function of beach in front of the levee. Upon comparing the visual inspection photographs and flood control records, there were levee protection facility such as protection blocks located by the levee, so it would be able to supplement the insufficient protection function of beach in front of the levee. Therefore, the regular patrol should be maintained in the follow-up stage, and pay attention to the damage situation of protection blocks in front of the levee, in order to grasp the condition of beach in front of the levee. Upon considering that there were only 19 abnormal places in the range of this project which should be observed continuously, most of damages were the crack, parts of damaged positions had already been detected with slightly cavity signal. The large area peeling mold rebuilding way would be used as the main repair method. As for the parts with smaller crack width and depth, the crack digging and filling way would be used as the main repair method, in order to prevent the exterior water from invading the levee body continuously. Other damages belonged to the surface damage, only local repair way was needed for relevant repairing. There were 19 damaged places in this project by visual inspection, the estimated repair fee is about NT$ 3,575,000.