• Journal of the Korean Geosynthetics Society
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• v.8 no.2
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• pp.47-54
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• 2009

The ballast track, the most common type of conventional railroad track in Korea, is deteriorated by abrasion of ballast, it's penetration into roadbed, and rugged surface of roadbed caused by cyclic loading of train. Persistent occurrence of those phenomena lead to insufficient drain capacity, one of major factors in track design, and it increases pore water pressure and decreases of shear strength under rainfall condition leading to unstable roadbed. In this study, cylindrical model tests are executed for 3 types of geotextile applying cyclic loading in order to observe the characteristics of displacement and bearing capacity of geotextile, and undrained condition has been applied for 0 day, 3 days and 7 days to each geotextiles. The results showed that there was about 1% difference at the final displacement rates between reinforced soils and nature soils and the displacement of the ground surface increases along with the degrees of the saturation. And in case that water contents exceeds the threshold, it is also apparent that weight and tensile strength of geotextile influences displacement of the ground surface. And the larger weight of geotextile is, the smaller plastic displacement. It is evaluated that non-woven fabric comes into effect on reducing the bearing capacity but, the weight of geotextile has little influence on it.

• Geotechnical Engineering
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• v.14 no.5
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• pp.205-218
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• 1998

The purpose of this study is to develop and utilize new assessment of liquefaction potential based on DSC(disturbed state concept) and dissipated energy concept. The term liquefaction has suddenly loses its shear strength and behaves like a fluid. Liquefaction has been a source of a major damage during severe earthquake. In this study, the cyclic undrained behavior of Joomoonjin strand is investigated by using an automates triaxial testing device(C. K. Chan type). In order to assess liquefaction potential of saturated strand, DSC method and energy method are applied for the experimental data. The use of DSC method and energy method to define the liquefaction potential is verified through laboratory testis of cyclic triaxial test on saturated sand specimens. Based on the analytical results of DSC method, the relationship between the factor affecting liquefaction characteristics(Dr) and physical properties of the saturated santa(fs and D.) is found. Based on the analytical results of energy method, it is found that the initial liquefaction of rand is related to the significant change in the dissipated energy. Finally, it is shown that the DSC method and energy method can capture the liquefaction mechanism.