| 摘要: | 本研究主要探討初始應力、應力增量、及不同水力坡降下對土壤-不織布系統過濾行為之影響。本研究為模擬鐵路或道路邊溝排水系統，上層土壤採用粉土質砂土、下層模擬粗顆粒排水層，採用均ㄧ直徑15.85 mm不鏽鋼珠所排列而成，並使用地工織物當分隔層，進行動態過濾試驗，探討土壤-地工織物系統承受動態荷重後其過濾行為之變化。
本研究採用化學黏合不織布進行試驗，試驗採用初始應力0、24.5 kPa、49 kPa、98 kPa、196 kPa，應力增量採用0、24.5 kPa、98 kPa、196 kPa，並控制頻率0.1赫茲及荷重作用次數5000次；試驗時當承受動態荷重時記錄其作用應力、時間、及土壤沉陷量，而後進行透水試驗，紀錄當時溫度與滲流量，試驗後量測土壤流失量；將試驗所得之滲流量、滲透係數、土壤孔隙比進行分析與討論。
試驗結果顯示：(1)當初始應力24.5 kPa應力增量0與初始應力0應力增量24.5 kPa及無荷重試驗結果相較，其系統最終滲流量與滲透係數最大差異性為20 %，顯示當土壤承受總應力24.5kPa以內，其過濾行為與無荷重時差異不大。(2)土壤-不織布系統最終滲流量及滲透係數隨初始應力或應力增量增加而上升，顯示不織布與不鏽鋼珠界面因動態荷重作用造成不織布受張力作用，因而織物有效開孔徑增大，造成系統最終滲流量與滲透係數上升。(3)由全部試驗總結，系統滲流量與滲透係數皆隨總應力增加而增大，且隨總應力增加，滲流量與滲透係數增量有下降趨勢，但與水力坡降並無關係。系統僅承受初始應力98 kPa及196 kPa試驗可發現，因土壤壓縮程度已達極限，故最終滲流量與滲透係數增量已不明顯。(4)由總應力98 kPa與總應力196 kPa試驗結果顯示，當系統同時承受初始應力與動態應力增量時，將提高系統之滲流量與滲透係數；僅承受動態應力增量時，系統之滲流量與滲透係數次之；僅承受初始應力時，系統之滲流量與滲透係數為最低。(5)各試驗後之土壤孔隙比顯示，土壤孔隙比隨總應力增加而降低，但滲流量與滲透係數不隨土壤孔隙比降低而降低，故動態載重對土壤-織物系統之過濾行為影響甚大。
In this research, in order to understand filtration behavior of soil-nonwoven geotextile under cyclic loads, proceeding dynamic filtration test according to ASTM D4716 constant head test and improve it. The test specimen contains: (1)Sandy-soil with 14 % fine particles on upper levels, (2)Nonwoven Geotextile sealed by clamping a pair of steel rings, (3)In order to simulate road or railroad edge drain system, using stainless beads with the same diameter 15.85 mm on the bottom. Discuss the influence of the filtration behavior of soil-nonwoven system after dynamic filtration test on sustained loads, increment of stress and varied gradient ratio (i = 1, 5, 10). This research use chemical-bonded geotextile for the tests and adopted four sustained loads(0、24.5、49、98、196 kPa), four increment of stress (0、24.5、98、196 kPa), are controlled at 0.1 hertz and 5000 times of cyclic loads.
The results show: (1)While total stress no more than 24.5 kPa, the filtration behavior can be explained to no variation with the test without load. (2)Because of the interaction between geotextile and stainless beads, apparent opening size of geotextile is increased by tension force, besides cause flow rate of discharge and permeability rising by increasing initial stress or increment of stress. (3)As the total stress rises, the flow rate of discharge and permeability decline. (4) The test results of total stress 98 and 196 kPa shows when subjected to initial stress and increment of stress at the same time, it supply to highest flow of discharge and permeability; when subjected to only increment of stress, it supply to middle flow of discharge and permeability; when subjected to only initial stress, it supply to lowest flow of discharge and permeability. (5) Void ratio decreased with the increasing of total stress, but not the flow of discharge and permeability. |
