張力作用對織物開孔徑之變化及其過濾特性之探討

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Title:	張力作用對織物開孔徑之變化及其過濾特性之探討
Other Titles:	The influences of tensile stress on pore size distribution and filtration characteristics of geotextiles
Authors:	王瑞鴻;Wang, Ruei-hung
Contributors:	淡江大學土木工程學系碩士班吳朝賢;Wu, Cho-sen
Keywords:	坡降比試驗;地工織物;張應變;有效開孔徑;透水速率;Gradient ratio test;Geotextiles;Tensile strain;Apparent opening size;Flow velocity
Date:	2006
Issue Date:	2010-01-11 05:20:03 (UTC+8)
Abstract:	本研究使用兩種織布及兩種不織布於未伸張及張應變為5%、10％、20％時，進行變水頭透水速率量測、濕篩法開孔徑量測、及改良ASTM D5101之GR試驗儀；以連續變換水力坡降進行土壤-地工織物系統坡降比試驗，以探討織物於未伸張及張應變下之坡降比值及滲流量變化。試驗結果以織物有效開孔徑、透水速率變化、GR值、系統滲流量及土層滲透係數進行比較與討論。織物開孔徑量測結果顯示，織布與不織布的開孔徑皆隨張應變之增加而增加，兩種不同厚度及單位重的織布，其開孔徑分佈曲線有相似的趨勢，即開孔徑於織物張力最大值之前變化較小，當伸張超過最大張力值後則有明顯增加的現象。兩種不同厚度及單位重的不織布，由未伸張至張應變為20％(本研究之最大張應變)之開孔徑分佈曲線有明顯的差異，厚度較大的織物開孔徑隨張應變之增加而增大的趨勢較緩，代表織物的開孔徑變化與厚度及單位重有關，四種織物的有效開孔徑與張應變成線性關係。透水速率試驗結果顯示，織布與不織布的透水速率皆隨張應變之增加而增加，其中織布在張力達最大值之前透水速率與張應變呈線性增加，超過張力最大值後則變化較大。不織布材料的透水速率隨張應變增加呈近似線性關係增加。厚度較大的織布及不織布透水速率試驗結果皆呈現較小的變化，主要為張力作用下開孔徑變化較小所導致。坡降比試驗結果顯示，相同的水力坡降下，隨張應變的增加GR值上升幅度有隨之降低的趨勢，系統滲流量及土層滲透係數k13 及k35有隨之增加的趨勢。相同張應變下，GR值、土層滲透係數k13 及k35隨試驗延時增加有逐漸上升的現象，系統滲流量隨水力坡降增加有逐漸增加的現象，土層滲透係數k13 及k35隨試驗延時增加有逐漸降低的現象。 The influences of unidirectional tensile stain on pore size distribution and filtration characteristics of geotextiles were investigated in this study. Apparatus have been designed and built for determining pore size distribution, measuring flow rate through plain geotextile, and conducting a gradient ratio test. A unidirectional strained geotextile specimen was secured by clamping a pair of steel rings on the specimen; three experiments were carried out collaborated with the clamped specimen. Four geotextiles, two nonwoven and two woven, were employed in this study. The geotextiles were stretched to 5%, 10% and 20% strains prior to installation in apparatus. The experimental results show: (1) For all tested geotextiles, linear function appears to be appropriately in describing relationship between the AOS and the tensile strain. The pore size distribution curves corresponding to 20% strain for both woven geotextiles are distant from the other three curves corresponding to lower strains. (2) There is a growth in the flow rate through the plain geotextile, which is proportional to the magnitude of the tensile strain as the strain is lower than one corresponding to the peak tensile strength. A remarkable increase in flow rate for both woven geotextiles strained at 20% strain is noted, which can be associated to the distinctive pore size distribution. Tensile strains corresponding to peak strength are 11.8% and 14.3% for woven geotextiles W1 and W2. Significantly different behavior of W1 and W2 geotextiles at 20% strain from that of the lower strains may be contributed to the over-straining of woven geotextiles. (3) Under a specific hydraulic gradient, increase of the tensile strain reduces the gradient ratio; the effect is more pronounced for nonwoven geotextiles. The stable flow rate for the system collaborated with stretched geotextile relative to the un-stretched geotextule increase with the increase of the tensile strain except for NW1 geotextile at 5% strain and i=5 condition.
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