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    jsp.display-item.identifier=請使用永久網址來引用或連結此文件: https://tkuir.lib.tku.edu.tw/dspace/handle/987654321/34601


    题名: 動態荷重對土壤 : 地工不織布過濾行為的影響
    其它题名: The influence of cyclic loads on filtration behavior for soil-nonwoven geotextile composite
    作者: 楊蕙旭;Yang, Hui-hsi
    贡献者: 淡江大學土木工程學系碩士班
    吳朝賢;Wu, Cho-sen;洪勇善;Hong, Yung-shan
    关键词: 動態滲透試驗;靜載應力;動態應力;地工織物;過濾行為;Filtration Test;Sustained Load;cyclic Load;Geotextiles;Filtration behavior
    日期: 2009
    上传时间: 2010-01-11 05:25:16 (UTC+8)
    摘要: 本研究主要探討靜載應力、動態應力、及不同水力坡降下對土壤-不織布系統過濾行為之影響。本研究為模擬鐵路或道路邊溝排水系統,上層土壤採用粉土質砂土、下層模擬粗顆粒排水層,採用均ㄧ直徑15.85 mm不鏽鋼珠所排列而成,並使用地工織物當分隔層,進行動態過濾試驗,探討土壤-地工織物系統承受動態荷重後其過濾行為之變化。

    本研究採用化學黏合不織布B進行試驗,試驗採用靜載應力0、49 kPa、98 kPa、196 kPa,動態應力採用0、49 kPa、98 kPa、196 kPa,並控制頻率0.1赫茲及荷重作用次數5000次;試驗時當承受動態荷重,記錄其作用應力、時間、及土壤沉陷量,而後進行透水試驗,紀錄當時溫度與滲流量,試驗後量測土壤流失量;將試驗所得之滲流量、滲透係數、土壤孔隙比進行分析,並與何俊宏(2007)試驗所採用之不織布A加以討論。

    試驗結果顯示:(1)根據何俊宏(2007)試驗結果顯示土壤-不織布A系統之過濾行為,其最終滲流量及滲透係數皆隨載重增加而上升。土壤-不織布B系統承受靜載應力或動態應力作用下的過濾行為,其系統最終滲流量與滲透係數皆隨載重的增加而逐步降低。 (2)土壤-不織布B於靜載應力與動態應力同步作用下,當總應力增至147 kPa時產生轉折點,土壤-不織布B組合系統的滲流量及滲透係數不減反增,達到穩定的時間也增長。 (3)延時過濾試驗達4個工作日以上,其滲流量及滲透係數於長期過濾行為下,雖隨時間漸趨於穩定,但無法明確知道土壤-地工織物系統之濾層已形成,或是因為微生物滋長形成一天然生化濾層而使水流逐漸降低。 (4)由總應力98 kPa與總應力196 kPa試驗結果顯示,當土壤-不織布B系統同時承受靜載應力與動態應力時,將提高系統之滲流量與滲透係數;僅承受靜載應力時,系統之滲流量與滲透係數次之;僅承受動態應力增量時,系統之滲流量與滲透係數為最低。 (5)在低應力作用下,土壤-不織布B系統滲流量與滲透係數隨孔隙比降低而下降,但在較高應力作用下系統之滲透係數卻隨土壤孔隙比之降低(載重增高)而上升,顯示動態載重對土壤-織物系統之過濾行為影響甚大。(6)於較薄的不織布A載重過濾試驗中,部分面積受張應力作用使得開孔徑增大,大於土壤孔隙比對土壤過濾行為的影響。厚度較大的不織布B,土壤受荷重孔隙比降低,導致滲流量及滲透係數隨之降低。當土壤-不織布B系統作用超過一定值之載重時,因不織布B開孔徑增大而增高之滲透性,大於土壤壓縮所降低的滲透性。
    The influence of load type on the filtration behavior for soil-nonwoven geotextile composites was studied and the results presented in this paper. The soil-geotextile composite was formed by inserting a piece of nonwoven geotextile between a 5-cm thick soil and a layer of steel beads. A heat-bonded nonwoven geotextile was used in this experimental test. Three load types, sustained load only, cyclic load only and cyclic load acting on a composite subjected to a sustained load, were applied to the composite prior to the filtration test. The frequency of the cyclic load was 0.1 Hz and 5000 cycles of repeated load was applied. Following the completion of a specific type of loading, water was allowed to flow through the composite from the soil into the drainage layer with various hydraulic gradients. A stable flow rate corresponding to each hydraulic gradient was measured. The averaged permeability value evaluated using Darcy’s law represents the filtration characteristics of the soil-geotextile composite. Test results were compared with those of a thinner nonwoven geotextile.

    The experimental results show: (1) By averaging the permeability values for the soil-geotextile layer (the combined 2.5-cm soil length and geotextile thickness) and the soil alone layer (2.5 cm) from the GR test, the averaged values for low, medium and high hydraulic gradients are close to those obtained from present test apparatus conducted on the 5-cm thick soil and geotextile composite. This result indicates that the present test apparatus produced a result comparable to the GR test result for the unloaded soil-geotextile system. (2) For the soil-geotextile composite subjected to sustained loads, the thinner geotextile composite subjected to greater sustained load resulted in a higher averaged permeability value. However, the increase trend subsides at high sustained load, especially for composites tested at high hydraulic gradients. (3)The thicker geotextile composites have opposite response to sustained load; the greater sustained load produced a lower averaged permeability value. (4) For thinner geotextile composites, free of sustained load or subjected to 98 kPa sustained load, the averaged permeability value increased with the increase in cyclic load. For composites subjected to identical cyclic loads, the composites tested under the 98 kPa sustained load produced greater averaged permeability values than those tested free of sustained load. (5) For thicker geotextile composite tested free of sustained load, the averaged permeability value decreased with the increase in cyclic load. (6) For thicker geotextile composite tested under 49 or 98 kPa sustained load, the averaged permeability value decreases with the increase in total load while the total load is less than 147 kPa, however, the trend reversed while the composite subjected to a total load exceeding 147 kPa. (7) Different amounts of soil particles were washed through the geotextile, however, no consistent relation between soil loss mass and magnitude of load could be found. (8) The void ratio of the composite decreased linearly with the increase in total load, but the averaged permeability value of the composite increased with the increase in total load, which is coinstantaneous with the decrease in void ratio. This contradicts the pure soil characteristics attributed to the combination of geotextile in-plane strain and cyclic load pumping action.
    显示于类别:[土木工程學系暨研究所] 學位論文

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