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    Title: 聲波監測應用於地錨結構破壞之模擬和訊號分析
    Other Titles: Simulation and signal analysis of ground anchor failures with application of acoustic monitoring system
    Authors: 鄭世豪;Cheng, Shih-hao
    Contributors: 淡江大學土木工程學系博士班
    張德文;Chang, Der-wen;李維峰;Lee, Wei-feng
    Keywords: 地錨;聲波監測;集中質塊法;訊號分析;損傷;ground anchor;acoustic monitoring;lumped mass method;signal analysis;distress
    Date: 2009
    Issue Date: 2010-01-11 05:22:05 (UTC+8)
    Abstract: 地錨工程技術因可充分發揮錨碇地層承載力、提高錨碇地層強度、減輕錨碇結構或支撐結構自重等優點,廣泛應用於交通建設的隧道開挖支撐;水壩和輸電塔的基礎穩定;邊坡穩定修護等大型建設工程。然而,由於其作用機制複雜且埋置於地層中,常因施工品質不良、鋼腱腐蝕、地層潛變或環境氣候變遷等外在因素影響造成缺陷,進而降低其服務年限和使用功能,故如何評估其耐久性和使用性能遂為現代地錨工程之重要工作。
    有鑑於此,本研究以現地拉拔試驗配合SoundPrint®預力連續式聲波監測系統,同步觀察地錨損傷發展和聲訊表徵,由試驗結果得知,監測系統之聲訊資料庫(各式材料損傷聲訊)和定位方式(時間差定位),可良好應用於地錨損傷情況和位置的鑑別,以利日後之維護補強和安全檢查之用。
    同時,地錨損傷過程複雜且依環境與肇因不同而有異,有限之試驗數據不易釐清,故吾人另基於聲波沿最短和最快路徑之假設,以集中質塊法為基礎建立數值分析模型,藉地錨損傷情況發展和聲洩訊號的模擬,瞭解各式設計地錨之受力分佈情形、損傷發展及特徵,以擴充其應用性和提出相關建議,希冀建立開創性的試驗成果和理論,供各界參考應用。此外,為進階探索試驗和理論損傷聲訊之隱藏內涵,本研究依訊號分析方法的比較,建議試驗聲訊應由數據的重疊分段和加窗處理消除主頻峰值兩側漣波,以增進其特徵判讀。最後,更透過試驗和理論聲訊的交义驗證,建立各式地錨之損傷規則和變化特徵,建議以結構損傷釋放音量和主要頻率,鑑別系統的損傷程度,回饋於設計和冀望落實於地錨維護管理之用。
    Geotechnical engineering of ground anchors is widely applied in many large-scale constructions, including tunnel excavation or support work on traffic construction, foundation stabilization work of dams and power transmission towers, slope stability work and so on. The causes are its many advantages in enhancing the load bearing as well as the strength of anchorage stratum and in decreasing self weight of anchorage structure and support structure. However, external factors such as poor quality of construction, tendon corrosion, creep stratum, and the change of climate can have serious defects on ground anchors, mostly embedded and thus have a highly-complicated mechanism action. In consequence, the service life and usage function of ground anchors can be greatly reduced. For this reason, evaluation of ground anchors’ duration and usage performance is of high significance to the temporary geotechnical engineering practice of ground anchors.
    In view of the circumstances mentioned above, this research draws on field pullout tests and SoundPrint® acoustic monitoring system to observe simultaneously the development of ground anchor distress and characteristics. As shown by test results, the database (from the various material defects of sound signals) and localization (time difference localization) of acoustic monitoring can be fairly used in discerning the ground anchors’ distress and location for bettering future maintenance work and safety inspection.
    In the meantime, the distress of ground anchors is essentially highly complex and can vary from different environmental conditions and causes. It becomes extremely difficult to recognize the failure behavior of ground anchors by using test data narrowly. Therefore, based on the presumption that sound wave follows the shortest and fastest path, this study applies lump mass model to establish numerical analysis. By looking at the development of ground anchors’ distress and acoustic simulation, the stress distribution of anchors of different designs as well as distress development and characteristics are discussed. In the attempt to achieve wider applicability and to provide more practical suggestions, this research seeks a breakthrough of test results and theory for the usage of practical engineering. Accordingly numerical analysis is used to further explore the hidden meaning of experiment signal and numerical signal, and the signal of experiment is suggested to be obtained through the piecewise of overlapping and by joining window function to eliminate the two-side of main amplitude in order to improve judgment of their characteristics. Last, to overlap verify experiment signal and numerical signal in establishing the regular pattern of distress and characteristic changes on anchors of different types, it is suggested to use the acoustic volume release and nature frequency of structure distress in distinguishing distress degrees. The principal research aims to contribute to the succeeding work of anchor designs and to more promised effects of anchor maintenance.
    Appears in Collections:[Graduate Institute & Department of Civil Engineering] Thesis

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