PURPOSES: The purpose of this study is to identify the road-subsidence mechanism in unsaturated sandy soils. METHODS: A series of soil chamber tests were conducted under various conditions. RESULTS: The cavity-expansion characteristics in unsaturated sandy soils due to seepage were affected by the outlet size, seepage intensity, relative density, and fine content. CONCLUSIONS: In unsaturated sandy soils, the cavity-expansion speed was affected by the outlet size, relative density, seepage intensity, and clay content; however, the cavity-expansion shape was very similar. As the outlet size and seepage intensity increased, the cavityexpansion speed increased. As the relative density increased, the cavity-expansion speed increased because of a sudden decrease in shear strength, resulting from the increased saturation (reduction of matric suction). The cavity expanded faster with the increasing clay content, up to a certain threshold. It expanded at a slower rate once it passed the threshold. Finally, it reached a stable state where the cavity did not expand due to seepage.

본 연구에서는 불포화 투수계수를 측정하기 위하여 Klute(1965a)에 의하여 제안된 정적측정방법의 원리에 axis-translation의 기법을 적용하여 새로운 실험장치를 개발하였다. 이 실험장치는 모관흡수력(matric suction)의 증가에 따른 함수특성과 투수계수의 변화를 동시에 측정할 수 있도록 설계되었다. 실험에는 불포화 투수특성과 No.200체 통과 세립분의 상호관계를 규명하기 위하여 각각 세립함유량이 7.3%(인주), 19.6%(성환)