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.

ABSTRACT
 1. 서론
 2. 모형토조 시험장치 및 시험절차
 3. 시험시료
 4. 시험결과 및 분석
  4.1. 불포화토 지반의 동공 발생 및 확장 형태
  4.2. 함몰에 대한 유출구 크기의 영향
  4.3. 함몰에 대한 침투유량의 영향
  4.4. 함몰에 대한 상대밀도의 영향
 5. 결론
 REFERENCES

• 권기철(동의대학교 토목공학과 교수) | Kweon, Gichul 교신저자