正向載重下針軋不織布的透水行為

探討現地環境下過濾系統(現地土壤-織布-排水層)在正向力作用下的相關研究甚少，本研究使用五種不同的針軋不織布，於織布上下游處放置鋼珠，以模擬土壤顆粒及排水層，並在上方施加正向應力，探討正向應力與鋼珠尺寸對織布透水特性之影響。先測定織布的基本性質如單位面積質量、厚度等，再使用正向載重下透水量測儀器，量測定水頭試驗與變水頭試驗下織布之透水量。最後利用拓印的方式量測不同尺寸鋼珠下針軋不織布與鋼珠的接觸面積。使用達西定律或是Hufenus and Schrade經驗公式分析透水性結果顯示，針軋不織布在上下游鋼珠尺寸不變，僅改變正向應力時，隨著正向應力的增加，織布變緊繃，透水性會變小。當下游鋼珠尺寸不變，施加正向力也相同的情況下，隨著上游鋼珠由大至小，透水性也有越來越小的趨勢。另外單位面積質量較小、厚度較薄的織布(如NW1、NW2、NW3)透水性會受到下游鋼珠尺寸改變的影響；而單位面積質量較大且厚度較厚的織布(如NW4、NW5)透水性則幾乎不變，完全不受下游鋼珠尺寸的影響。在增加載重的過層中，低正向載重下是透水性減少最劇烈的區間，隨載重增加減少量逐漸趨緩。在鋼珠對針軋不織布接觸面積的量測中，低載重在織布上時，鋼珠的接觸面積增加的幅度也是最多，之後加載增加幅度也會趨於減少。 Giroud (1996)所提出預測透水性之經驗式與本研究試驗結果相互比較顯示，在有載重時厚度初始值為2.1 mm(NW2和NW4)時實驗值跟經驗式是非常接近的。在其他厚度時，當上游鋼珠尺寸越小時，其結果會越接近經驗式；上游鋼珠尺寸越大時，其結果會越遠離經驗式，並使用公式反推形狀因子發現如果使用Giroud (1996)提出的形狀因子延伸得到孔隙率0.8以下的結果是會低估的。最後給予實務工程上對針軋不織布放入系統後，可以使用的折減係數。

關鍵字

針軋不織布；透水性；正向應力；鋼珠尺寸

並列摘要

Five needle-punched nonwoven geotextiles were employed in this study to investigate the effect of normal stress on flow capability of needle-punched nonwoven geotextiles. Different sized steel beads were placed upstream and downstream of a geotextile specimen to simulate soil particles and drainage layer in a field drainage system application. Flow rate of the steel beads-geotextile-steel beads system under constant and falling head tests were measured and analyzed. Darcy's law and Hufenus and Schrade empirical analysis were adopted to calculate permittivity of the geotextiles under tested. The results show that permittivity of the geotextiles decreases with the increase of normal stress, permittivity of the geotextiles decreases with the reduction of upstream steel bead size, the size of downstream steel bead has insignificant effect on the permittivity of the thicker and heavier geotextiles, most of the permittivity reduction occurs as low normal stress applied on the system. Giroud (1996) proposed the empirical formula of the present study show results compared with each other, There load in the thickness of the initial value of 2.1 mm (NW2 and NW4) when the experimental values with the empirical formula is very close. When the thickness of the other, when the upstream beads size is smaller, the result will be closer to the empirical formula; Upstream beads larger the size, the result will be farther away from the empirical formula. And a formula to strike a shape factor, It found that if Giroud (1996) presented the results obtained form factor extension of porosity of less than 0.8 will be underestimated.. The last reduction factor obtained by the study.

並列關鍵字

non-woven ； beads size ； permittivity ； normal stress

參考文獻

1. 賴建斌(2015)，“正向載重下針軋不織布的開孔徑分佈”，淡江大學土木工程研究所碩士論文，台北。

6. Gourc, J. P., Giroud, J. P. and Aubert, V. (2012). Theoretical model for the hydraulic properties of geosynthetic drainage materials. Geosynthetics International, 19, No. 2, 183–190.

7. Giroud, J. P. (1996). Granular filters and geotextile filters. GeoFilters’96, Lafleur, J. and Rollin, A. L., Editors, BiTech, Montreal, Canada, pp. 565–680.

8. Hufenus, R.and Schrade, U. ,2006,“An optimized method measure the hydraulic conductivity of geosynthetics under load”. Geotextiles and Geomembranes, vol.24 pp.243-253

10. Palmeira, E.M. ,Tatto J and Araujo G.L.S. ,2012,“Sagging and filtration behavior of nonwoven geotextiles overlying different bedding materials”. Geotextiles and Geomembranes, vol.31 pp.1-14

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正向載重下針軋不織布的透水行為

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