本研究使用三種不織布於未伸張及張應變為2%、5%、7.5%、10％及20％時，進行單、雙向拉伸試驗、變水頭透水速率量測、濕篩法開孔徑量測、及顯微鏡觀察，以探討織物於未伸張及張應變下之開孔徑及透水速率變化。 拉伸試驗結果顯示，當拉伸至相同應變時，雙向拉伸試體的張力值會比受單向拉伸的試體大。不織布拉伸達最大張力值時，單向拉伸三片不織布A、B、C的平均應變值分別為60.5%、50.5%及59.3%，遠大於發生在雙向拉伸試體的26.6%、24.1%及29.8%。織物A、B、C試體受單向拉伸之最大張力值的平均分別為7.7、9.4和12.9 kN/m，雙向拉伸最大值的平均分別為6.0、8.5和13.2 kN/m。 透水速率試驗結果顯示，三種不織布的透水速率皆隨張應變增加至5%而逐漸降低，但拉伸在較大應變區間(7.5%~20%)時透水速率隨應變增大而加快。在相同張應變程度的拉伸下，針軋不織布隨著厚度的增加，透水速率越慢。兩種不同拉伸方式對三種不織布的透水速率的影響，是在相同應變下，織物經雙向拉伸後的透水速率都會比單向拉伸試體快。透水速率隨著拉伸應變的增加而降低後再上升，最低的透水速率都發生在5%張應變。 織物開孔徑量測結果顯示，三種不織布的開孔徑皆隨張應變之增加而減少，三種不同厚度及不同拉伸方式的織物，其開孔徑分佈曲線有相似的趨勢，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，織物厚度增加開孔徑逐漸減小，代表織物的開孔徑變化與厚度及張應變有關。顯微鏡下的觀察可見，張應變增大時，同焦距鏡頭下可清晰觀察到的纖維數增多；三種不織布的孔隙面積皆顯現隨應變的增加而減小及減少。 The influences of uniaxial and biaxial tensile strain on pore size distribution and seepage rate of needle-punched geotextiles were investigated in this study. Apparatus have been designed and built for conducting uniaxial and biaxial stretching test of geotextiles, determining pore size distribution, measuring flow rate through plain geotextile and observing variation of fiber with microscope. A uniaxial and biaxial strained geotextile specimen was secured by symmetrical clamping apparatus; two experiments were carried out collaborated with the clamped specimen. Three needle-punched nonwoven geotextiles were employed in this study. The geotextiles were stretched to 0%,2%,5%,7.5%, 10% and 20% strains prior to installation in apparatus. The experimental results show: (1) For all tested geotextiles when stretched to the same strain, the tensile strength of geotextiles sustained of uniaxial loading is always smaller than geotextiles sustained of biaxial loading. For three nonwoven geotextiles specimen sustained a peak tensile strength of 7.7﹑9.4 and 12.9 kN/m uniaxial load observed an average strain of 60.5%﹑50.5% and 59.3% respectively and is much higher than that of specimen sustained a peak tensile strength of 6.0﹑8.5 and 13.2 kN/m of biaxial load with average strain of 26.6%﹑24.1% and 29.8% respectively. (2) It appears slow down in the flow rate through the plain geotextile till 5% strain; on the contrary, a growth in the flow rate after 7.5% strain and a remarkable increase in the flow rate for all geotextiles at 20% strain is noted significantly the same behavior for uniaxial and biaxial sustained loading. (3) For all tested geotextiles, a decreasing function appears to be appropriately in describing relationship between the O95 and the tensile strain and thickness of geotextiles, increase of the tensile strain and thickness of geotextiles result in reduces of O95. The pore size distribution curves corresponding to 20% strain for three nonwoven geotextiles are distant from the other three curves corresponding to lower strains.
