連續纖維加勁砂土抗剪行為

Shear Behavior of the Sand Reinforced with Continuous Fibers

吳泰慶(Tai-Ching Wu)

指導教授 ： 陳榮河

國立臺灣大學/工學院/土木工程學研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.00972

摘要

纖維加勁土壤工法是較為少見的加勁工法，其係藉由土壤與纖維的互制作用，提升土壤的抗剪強度，並能配合植生工程，提高生態性及美化環境景觀。
本研究的目的在於探討纖維加勁土壤之抗剪機制，藉由直接剪力試驗分別以纖維之型式（連續纖維及離散纖維或稱短纖維）、含量、線徑以及相對於剪切面之排列方向作為控制變因，探討各項變因對纖維加勁土壤之影響。另外，利用冰凍法將試體定型，觀察試體受剪後內部纖維的變形，以了解纖維排列方向對其受剪行為之影響。
根據試驗結果顯示，在纖維含量固定時，連續纖維加勁土壤之加勁強度較離散纖維加勁土壤大，且更具韌性；另外，纖維的加勁強度會受正向應力影響，正向應力越大，加勁土壤之剪應力增量越大。且依正向應力不同，加勁土壤具有不同的最佳纖維含量，約介於1.5~2.5 %之間。故工程設計時，或可隨不同之覆土深度，設計不同之纖維含量；如覆土深度增加，纖維含量可予減少；另外，纖維線徑對加勁土壤之首峰剪力強度之影響並不明顯，僅在極限剪力強度（剪位移量為12 mm或剪應變量12 %時之剪應力）時，才有較明顯之差異；此時，若線徑越細，加勁試體剪力強度越高；除此之外，透過試驗後之試體剖面觀察，得知纖維之排列方向會影響纖維之變形行為，並使纖維發揮不同之拉力，進而影響加勁土壤之抗剪強度。

關鍵字

加勁土壤 ； 纖維加勁 ； 直接剪力試驗 ； 抗剪行為 ； 冰凍法

並列摘要

Fiber-reinforced soil technique uses fibers embedded in the soil to increase the shear strength of the reinforced soil through the soil-fiber interaction. In addition, the work can be vegetated for sustainable development of the environment. Thus, this technique provides an alternative structure that is safe, economic, as well as having more environmental amenity.
The purpose of this study is to investigate the shear mechanism of the fiber-reinforced soil through direct shear tests. The main variables for the tests include fiber type, fiber content, fiber diameter and fiber orientation. In order to investigate the effect of fiber orientation on the shear behavior, samples are frozen after testing to observe the deformation of fibers within the sample.
According to the test results, at the same fiber content, soil reinforced with continuous fibers have higher shear strength and more ductile than that with discrete fibers. In addition, the increased strength varied with the normal stress. Under different normal stresses, fiber-reinforced soils have different optimum fiber contents, ranging increases from 1.5 ~ 2.5%. Thus, theoretically, the fiber content may be reduced as the depth. Besides, the fiber diameter does not have a significant influence on the first peak of the shear strength of the reinforced soil, but it does affect its ultimate shear strength, with better effect for thinner fibers. In addition, the orientations of fibers influence the reinforcing effect as well.

並列關鍵字

Reinforced soil ； Fiber reinforcement ； Direct shear test ； Shear behavior ； Freezing method

參考文獻

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