Filtration behavior and micro-observation of geotextiles under bi-directional cyclic flow
Date Issued
2007
Date
2007
Author(s)
Chung, Wen-Bin
DOI
zh-TW
Abstract
地工織物在過濾與排水之應用上，已經十分廣泛。因此，在評估地工織物過濾功能的準則與試驗，業已發展至一定之程度。不過，在實際的狀況下，如河堤或護岸，水流對於土壤-地工織物系統之作用，常是反覆進出流動於土壤中。但目前在試驗上主要是以單方向之水流來進行地工織物過濾之研究，鮮少使用雙向反覆水流來模擬。
本研究主要是使用雙向水流儀，模擬現地水流狀況，探討土壤-地工織物系統之過濾功能。研究內容主要是承自前人探討不同細粒料含量與覆土壓力對於地工織物過濾行為之影響。試樣之配比分別為(1) 5%粉土與95%砂土、(2) 15%粉土與85%砂土、(3) 5%黏土與95%砂土。主要之覆土壓為70 kPa與140 kPa。週期水流為600秒、300秒、150秒、75秒。此外，為瞭解織物層數對於過濾行為的影響，本試驗另外進行雙層織物之試驗比對。並且於上述試驗完成後，利用立體顯微鏡進行織物阻塞狀況之顯微觀察。
試驗結果顯示：(1) 本研究中之所有試驗並無發生砂湧(boiling)的現象。故本研究所選用之配比可能為一臨界配比；(2) 細粒料含量與覆土壓力的確對於土壤-地工織物系統之阻塞程度有影響；(3) 覆土壓力對於土壤-地工織物系統中，細粒料的遷徙具有很大之影響。覆土壓力愈大愈可抑制細粒料之遷徙與移動；(4) 雙層織物對於整體之沉陷具有減緩的作用。推測是對於水流有削減的功用；(5) 雙向水流在固定水流流速下，經過長期作用，有形成暫時穩定之過濾層。
This research utilized a bi-directional flow apparatus to probe into the filtration function of the soil-geotextile system under the actual water current condition. The content of this studty is a continuation of another research, state the reference, that emphasized the influence on filtration behavior of using different fine particle contents and overburden pressures. Furthermore, the soil samples in this study were composed of Vietnam sand with 5-15%fine material. Two kinds of overburden pressures were used: 70 kPa and 140 kPa. Also, four kinds of flow periods were adopted: 600, 300, 150, and 75 seconds per cycle. In addition, to understand the influence of the number of geotextile layer to the filtration behavior, this experiment has employed another case involving a double-geotextile layer. And, after above-mentioned methodology was completed, a stereomicroscope was utilized to observe the clogging condition in the geotextile.
The results of the experiment are: (1) In all the test, boiling did not occur; (2) The fine particle contents and overburden pressures have shown influence to the degree of clogging of the soil-geotextile system; (3) It was found obvious that the dimension of overburden pressures influences the movement of the fine particle in the soil-geotextile system, and the the overburden pressure increment can limit the movement of fine particles; (4) The double-geotextile layering condition has served in slowing down the system’s settlement; and (5) Under the long-term stable bi-directional flow, the soil-geotextile system has chances of exhibiting a steady filtration layer temporarily.
Subjects
雙向水流
地工織物
過濾
細粒料遷徙
bi-directional flow
geotextile
filtration
fine particle migration
Type
thesis