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    題名: 載重對不織布-土壤系統過濾特性的影響
    其他題名: Influence of Load on Filtration Characteristics for Nonwoven Geotextile-Soil Systems
    作者: 吳朝賢;洪勇善
    貢獻者: 淡江大學土木工程學系
    關鍵詞: sustained load;Pulsatory load;Filtration test;Nonwoven geotextile;Permeability;Geotextile-soil system
    日期: 2011
    上傳時間: 2012-05-01 16:26:50 (UTC+8)
    摘要: 在道路工程的應用上,地工合成材外包於砂礫石排水溝渠、單面或雙面包裹多孔半堅硬塑殼之地 工複合材,作為排水邊溝,在此應用中地工合成材執行過濾之功能。目前的設計中,織物之透水能力 與開孔徑、及系統的阻塞潛能,皆是對未受力之織物進行量測,並以單向穩定水流進行滲流試驗。但 在道路工程應用時,地工合成材承受靜載重,以及來自於公路車輛、火車、或飛機的不同程度動態載 重。由於靜、動態載重均將對織物造成平面拉伸;因此,合成材是否能成功執行功能,取決於織物受 平面拉伸和動態載重下的阻留、滲流能力、和阻塞潛能。 由於地工合成材所組成的過濾或排水系統在動態荷載下有三種主要反應:土壤密實、織物受張力 改變開孔徑、和動態荷重對顆粒的抽吸作用。此三因素皆影響織物的阻留、系統的滲流能力、和系統 的阻塞潛能。因此,亟需進行地工合成材所組成的過濾系統在動態荷載下的過濾特性研究,並將三因 素造成的影響分離,如此才能在設計準則中作適當的規範,以確保織物應用的成功。 文獻顯示織物-土壤過濾系統的過濾特性,受到載重大小、頻率、和形式,和基層粒徑等的影響。 據此,本研究主要在探討模擬的路基土壤-織物-基底骨材系統受荷載後的過濾特性;荷載項目包括純 靜態載重、純動態載重、和靜-動態載重組合。本研究將選用4 種針軋不織布進行載重後的滲流試驗; 並以4 種不同尺寸的鋼珠粒徑置放於織物下模擬基底骨材,以深化骨材尺寸影響的探討。將以4-5 個 介於0-196 kPa 間的載重施加於路基土壤-織物-基底骨材系統。第三年的研究將延伸到不同動態載重頻 率對系統過濾行為的影響探討。
    Geotextiles have been widely used as a substitute for mineral materials to provide separation and filtration functions in roadway systems. In filtration applications the geotextile is used as a filter to prevent the undue migration of fine particles and allow adequate seepage to flow through the geotextile plane. Geotextile serves as a filter or separator in roadway applications must subject to earth pressure and dynamic or impact load caused by highway vehicles, railroad trains or landing aircraft. Therefore, the success of these applications depends on the retention and seepage capabilities of geotextiles, and the prevention of undue clogging as the geotextiles subjected to in-plane stress/strain and dynamic load. An in-plane strain can change the geotextile pore size with an associated reduction in its particle retention capability or a change in permeability. The fine particles in the subgrade may be pumped into the subbase by the dynamic load action. This action increases subbase course contamination. Thus, the current filter criteria may not be effective because the current filter criteria or the selection of suitable geotextiles is based on the pore size and permeability of plain geotextile. The clogging potential is also evaluated for an un-loaded soil-geotextile system. The load action can cause changes in soil compactness, geotextile stretching and flow interaction at the soil-geotextile interface. All of these load-induced changes on geotextile may affect the filtration behaviour of the soil-geotextile system. The impact of load type on the filtration behaviour of soil-nonwoven geotextile composites will be studied through series of tests using an experimental apparatus designed specially for the laboratory tests. In these tests, the soil-geotextile composite is fabricated by inserting a piece of nonwoven geotextile between a 5-cm thick soil layer and a layer of steel beads. One of the three load types, namely sustained load, pulsatory load, and compound load of pulsatory and sustained load, is applied to the composite prior to each filtration test. The frequency of the pulsatory load is 0.1 Hz and a total of 5000 cycles of repeated load applied to the composite for each load type test. After applying specific type of load on a soil-geotextile composite, water is allowed to flow down through the composite from the soil into a drainage layer set at various hydraulic gradients. The flow rates corresponding to elapsed times are measured and the averaged permeability value is extracted by using Darcy’s law to characterize the filtration performance of the entire soil-geotextile composite. Variations in the averaged permeability value with respect to the soil void ratio, magnitude and type of normal load are examined. This research conducts experimental tests that lead to the identification of factors dictating the seepage characteristics of soil-geotextile composite.
    顯示於類別:[土木工程學系暨研究所] 研究報告

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