動態載重頻率對土壤-地工不織布過濾行為的影響

機構典藏 > College of Engineering > Graduate Institute & Department of Civil Engineering > Thesis > Item 987654321/87850

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Title:	動態載重頻率對土壤-地工不織布過濾行為的影響
Other Titles:	The influence of cyclic loading frequency on filtration behavior of soil-nonwoven geotextile systems
Authors:	余仁浩;Yu, Jen-Hao
Contributors:	淡江大學土木工程學系碩士班吳朝賢;Wu, Cho-Sen
Keywords:	動態載重;加載頻率;土壤-地工織物複合系統;過濾行為;cyclic loading;frequency;soil-geotextile system;Filtration behavior
Date:	2013
Issue Date:	2013-04-13 11:48:14 (UTC+8)
Abstract:	為了模擬現地土壤、織物、排水材料受載重作用和加載頻率對排水溝渠過濾系統的影響，本研究進行動態載重下土壤-不織布系統之過濾滲透試驗，主要探討在不同水力梯度下載重作用、不同的加載頻率對土壤-不織布複合體系統過濾行為之影響。試驗土壤採用黏土質砂土，不織布下方利用不鏽鋼珠模擬粗顆粒排水層，採用均ㄧ直徑15.85 mm 排列而成，進行過濾試驗，根據試驗結果探討複合體系統承受載重及加載頻率作用後其過濾行為之影響。本研究採用一款針軋不織布進行試驗，試驗將進行系統未加載0 kPa以及靜態載重為40 kPa、65kPa、100 kPa，動態載重為35 kPa、70 kPa、100 kPa，作用頻率為0.1 Hz、1 Hz、2 Hz、5 Hz之組合，並控制載重作用次數為5000 次。試驗過程複合體系統承受載重頻率影響，並記錄其作用應力、時間、及土壤沉陷量。進行過濾試驗時，記錄試驗延時、系統沉陷量與滲流量，試驗後量測土壤流失量和織物上土壤殘留量，及根據實驗結果量測之流量、時間及水力梯度，利用達西定律 Q/t=q=kiA ，來求取流率(q)及滲透係數(k)以描述整體土壤-織物複合層的過濾特性，並進行相關分析與探討。試驗結果顯示，土壤-不織布複合體系統加載後，造成土壤試體壓縮，同時不織布也產生擠壓，不同的加載頻率將引起不織布產生相異之變化，加載頻率的快慢會影響土壤-不織布系統水流通過的能力，在低水力梯度時加載頻率1 Hz以下隨著載重越大而提高整體滲透性，而加載頻率2 Hz以上隨著載重越大而降低整體滲透性，因此加載頻率快慢將影響土壤-不織布系統過濾行為。高水力梯度下對整體的過濾行為影響逐漸減小，過濾行為逐漸接近純土壤行為。 Geotextiles are often subject to different load types in their filtration applications. The load action can cause changes in soil density, geotextile stretching and flow interaction at the soil-geotextile interface. All of these load-induced changes to a geotextile may affect the filtration behaviour of the soil-geotextile system. The impact of loading frequency on the filtration behaviour of soil-nonwoven geotextile combinations has been studied through a series of tests using an experimental apparatus designed specially for the laboratory tests. In these tests, the soil-geotextile combination was fabricated by inserting a piece of nonwoven geotextile between a 50 mm thick soil layer and a layer of steel beads. One needle-punch nonwoven geotextile was employed in this study. One of the three load types, namely sustained, pulsatory and a combination of both was applied to the combination prior to each filtration test. For the latter two load types, one of the loading frequencies, namely 0.1 Hz, 1 Hz, 2 Hz and 5 Hz was applied to the combination. A total of 5000 cycles of repeated load was applied to the combination for each load test. After applying this specific type of load on a soil-geotextile combination, water was allowed to flow down through the combination from the soil into a drainage layer set at various hydraulic gradients. The flow rates corresponding to elapsed times were measured and the average hydraulic conductivity value was extracted by using Darcy’s law to characterize the filtration performance of the entire soil-geotextile combination. Variations in the average hydraulic conductivity value with respect to the soil void ratio, magnitude and type of normal load were examined. The experimental results revealed that the void ratio of soil decreased with the increase of total load. For the water flows through the combination with low hydraulic gradient, hydraulic conductivity of the combination increases with the increase in total load if low loading frequency was applied to the system. Higher frequency produced reverse results, hydraulic conductivity of the combination decrease with the increase in total load. Loading frequency reduces its effect on the hydraulic conductivity of a soil-geotextile combination while water flows through the combination with high hydraulic gradient.
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