砂土液化後之剪力阻抗與剪應變之關係

本研究採取南投市貓羅溪沿岸曾經發生過液化區域之土壤，並利用GCTS (Geotechnical Consulting and Testing System)公司所設計製造的中空圓柱扭剪試驗儀進行中空反覆扭剪試驗。當試體發生液化之後持續對已經液化的土壤試體施予反覆或是單向度的剪應變，藉此觀察土壤在液化之後其剪力阻抗與剪應變之關係，同時比較反覆載重試驗與單向度試驗的方式所得到之液化後剪力阻抗與剪應變之關係，並將所得到之結果作為工程設計上之依據，使建築物在遭受輕度液化災害時不會有太大的損壞，而在發生中度災害後結構物經過修補即可再繼續使用，若是不幸遭遇極為嚴重的大規模液化，也能使結構物不會發生立即性的崩壞，以達到功能性設計之目的。本研究使總共進行了七組試驗，除了以現地土壤資料為基準重模而成之試體外，還有使用將從現地土壤中分離出來之粗料重模成相對密度為40%、64%與80%之試體。由試驗結果發現，單向度剪應變試驗與反覆剪應變試驗所得之結果只有在剪力阻抗開始上升後的初期有些微的不同，而不同剪動速率之反覆剪應變試驗結果也無太大的差別，因此在本研究中剪動的方式與速率並無太大之影響。而比較不同相對密度土壤的試驗結果，可以發現密度較小者受到較大的剪應變，剪力阻抗才開始增加，且剪力模數也比相對密度較高之土壤略低一點。至於比較不同細料含量土壤之試驗結果，可以推知細料含量較高者，液化後在較小之剪應變就開始提升其剪力阻抗但對剪力模數的影響不大。

關鍵字

砂；反覆試驗；剪應變；中空扭剪試驗；液化

並列摘要

There have been many researches on soil behavior after liquefaction in the recent years. In these studies, different soils were used and different loading condition were given to investigate the qualitative relationships between shear resistance and shear strain in liquefied soils. For the purpose of limiting excessive disturbances of soil fabrics after liquefaction and to maintain the condition at initial liquefaction, shear strain-controlled hollow cylinder torsional shear tests were performed in this research. After liquefaction, cyclic shear strain were exerted on the soil specimen to find out the relationship between shear resistance and shear strain in the liquefied soil of different relative densities and fines contents. Seven hollow cylinder torsional shear tests were conducted in this study. From the test results we found out that there is only a slight difference between monotonic shear strain test and cyclic shear strain test. In addition, the shear strain rate does not affect the shear stress-strain relationship after liquefaction. It was found that the specimen with lower density acquired its shear resistance after liquefaction at a larger shear strain and with a lower modulus then the specimen with higher density. The shear resistance start to rise at a smaller shear strain after liquefaction, but there is only a few changes in shear modulus.

並列關鍵字

soil ； cyclic test ； shear strain ； hollow cylinder torsional test ； liquefaction

參考文獻

[1] 吳紹華，2006，”砂土細料含量對動力三軸試驗超額孔隙水壓量測之影響”，台灣大學土木工程學研究所碩士論文。

[13] 余定縣，2004，“貓羅溪高細粒料土壤抗液化強度之研究”，台灣大學土木工程學研究所碩士論文。

[5] Ishihara, K. and Yasuda, S., 1975, “Sand liquefaction in hollow cylinder torsion under irregular excitation”, Japanese Society of Soil Mechanics and Foundation Engineering, Vol. 15, No. 1.

[7] Castro, G., 1975, “Liquefaction and cyclic mobility of saturated sands”, Journal of the Geotechnical Engineering Division, Vol. 101, No. GT6.

[9] Shamoto, Y., Zhang, J. M. and Goto, S., 1997, “Mechanism of large post-liquefaction deformation in saturated sand”, Soils and Foundations, Vol. 37, No. 2, pp. 71-80

國際替代計量

砂土液化後之剪力阻抗與剪應變之關係

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