坡降比試驗(Gradient ratio test, GR test)為評估土壤-地工織物阻塞潛能的方法之一，但此試驗並無考慮織物與粗顆粒排水層接觸之影響，因此坡降比試驗可能低估系統之阻塞潛能。本研究參考並修改ASTM D5101-90的水力坡降比試驗，設計可模擬現地試驗之透水試驗儀。並使用不同直徑之鋼珠以模擬粗顆粒排水層，進行過濾試驗，以探討織物下游粗顆粒排水層對阻塞潛能的影響。試驗結果顯示：最終滲流量之比例，並未與鋼珠底層開孔率之比例相同。而不同鋼珠直徑，開孔率相同時其GR值之差異並不大，顯示系統之阻塞應為底層開孔率所控制。 Gradient ratio test is one of the methods for evaluating the clogging potential of soil-geotextile system. However, GR test does not attend to the influence of clogging due to contact area existed between geotextile and coarse grain drainage layer. Gradient ratio test might underestimate the clogging potential of the drainage system. This paper aims to modify the hydraulic gradient ratio test of ASTM D5101-90, so that the permeable test apparatus can imitate the field condition and assess the influence of coarse grain drainage layer on clogging potential. The results of experiment show: the final seepage rate of the flow is not proportional to the opening area of the contact bottom. Bead of different sizes may form into the same opening area. However, GR does not change a lot as long as opening area remains the same. It shows that opening area instead of the bead size controls the clogging potential of drainage system.
第九屆大地工程學術研討會論文集=Proceedings of 9th Conference on Current Researches in Geotechnical Engineering