Journal of the Korean GEO-environmental Society (한국지반환경공학회 논문집)

Korean Geo-Environmental Society (한국지반환경공학회)
권호 표지
DOI QR코드

DOI QR Code

Consolidation Characteristics of Soft Ground with Artesian Pressure

피압에 따른 연약지반의 압밀 거동

  • Yun, Daeho (Department of Ocean Engineering, Pukyong National University) ;
  • Kim, Jaehong (Infrastructure Research Center, Korea Water Resources Corporation) ;
  • Kim, Yuntae (Department of Ocean Engineering, Pukyong National University)
  • Received : 2015.11.30
  • Accepted : 2016.01.21
  • Published : 2016.02.01
Download PDF
⟨ Previous Next ⟩

Abstract

Vertical drain has usually been used to accelerate the consolidation of soft clay deposits with high moisture content. Busan thick clay deposits are subjected to artesian pressure from an aquifer in sand and gravel layers. However, effect of artesian pressure existing in drainage-installed soft ground on consolidation behaviors is not well known. This paper investigates the consolidation behavior of drainage-installed soft ground at the Nakdong river estuary with artesian pressure and without artesian pressure. A series of one-dimensional large size column test was carried out to find out the consolidation characteristics of clay. Test results indicated that total settlement of clay with artesian pressure was higher than that without artesian pressure because effective stress decreased due to upward flow. Dissipation rate of excess pore water pressure delayed and excess pore water pressure did not fully dissipate in clay layer with artesian pressure. Undrained shear strength of clay ground with artesian pressure was lower than that without artesian pressure.

일반적으로 고함수비를 가진 연약지반의 경우 압밀 촉진을 원활히 하기 위하여 연직배수재를 주로 사용하고 있다. 부산 점토는 대심도 연약지반 아래에 존재하는 모래 및 자갈 대수층에 피압이 관측되었다. 그러나 연직배수재가 설치된 연약지반에 피압이 미치는 영향에 대한 조사나 연구는 미미한 실정이다. 따라서 본 논문에서는 연직배수재가 설치된 부산 낙동강 하구 연약지반에 피압의 작용 유 무에 따른 압밀 거동을 조사하기 위해 일차원 대형 컬럼 장치를 제작하여 점토지반의 압밀 거동 실험을 수행하였다. 실험 결과 최종 침하량은 피압이 작용하는 지반이 피압이 작용하지 않는 지반보다 더 크게 나타났다. 이는 피압의 상향침투로 인해 점토층의 유효응력이 감소하여 나타난 결과로 판단된다. 또한 피압이 작용하는 지반의 경우 과잉간극수압이 완전 소산되지 않고 잔류하는 것으로 나타났으며, 비배수 전단강도는 피압이 작용하지 않는 지반에 비해 상대적으로 낮은 값을 나타내었다.

Keywords

References

  1. Baek, S. H. (2002), Characterisation and geotechnical properties of Pusan clays by insitu tests, Doctor's thesis, pp. 1-165 (in Korean).
  2. Bergado, D. T., Manivannan, R. and Balasubramaniam, A. S. (1996), Proposed criteria for discharge capacity of prefabricated vertical drain, Journal of Geotextiles and Geomembrances, Vol. 14, pp. 481-505. https://doi.org/10.1016/S0266-1144(96)00028-3
  3. Chai, J. C., Mjura, N., Sakajo, S. and Bergado, D. (1995), Behavior of vertical drain improved subsoil under embankment loading, Journal of Soil and Foundation, Japanese Geotechnical Society, Vol. 35, No. 4, pp. 49-61.
  4. Hansbo, S. (1981), Consolidation of fine-grained soils by prefabricated drains, In Proceeding of 10th International Conference on Soil Mechanics and Foundation Engineering, Stockholm, Balkema, Botterdam, 3, pp. 677-682.
  5. Heo, D. Y. (2003), A study on the depositional environment and geotechnical properties of clay deposited at the busan new port site, Doctor's thesis, pp. 1-129 (in Korean).
  6. Holtz, R. D. (1987), Preloading with prefabricated vertical strip drains, Geotextiles and Geomembraens, Vol. 6, No. 1-3, pp. 109-131. https://doi.org/10.1016/0266-1144(87)90061-6
  7. Ismale, N. F. (1993), Laboratory and field leaching tests on coastal salt-bearing soils, Journal of Geotechnical Engineering, ASCE, Vol. 119, No. 3, pp. 453-470. https://doi.org/10.1061/(ASCE)0733-9410(1993)119:3(453)
  8. Jamiolkowski, M., Lancellotta, R. and Wolski, W. (1983), Precompression and speending up consolidation, Procedure of 8th European Conference, Soil Mechanics and Foundation Engineering, Vol. 3, pp. 1201-1226.
  9. Kim, H. T., Cho, J. H., Yoo, J. Y., Ro, J. K. and Kim, S. W. (2002), Self-weight consolidation settlement of soft-grounds on the artesian pressure after the penetration of vertical drain, KGS Fall '02 National Conference, pp. 597-604 (in Korean).
  10. Kim, S. K., Kim, H. I., Hong, B. M. and Kim, H. T. (1999), Consolidation analysis of vertical drain considering artesian pressure, KGS Spring '99 National Conference, pp. 62-69 (in Korean).
  11. Kim, Y. T. and Do, T. H. (2010), Effect of leaching on the compressibility of busan clay, Journal of Civil Engineering, Vol. 14, No. 3, pp. 291-297.
  12. Korea water resources corporation (2015), Subsoil investigation report of busan eco-delta city-phase 1 & area 3, pp. 1-468 (in Korean).
  13. Rixner, J. J., Kraemer, S. R. and Smith, A. D. (1986), Prefabricated vertical drains, Vol I, II and III: Summary of Research Report-Final Report, Federal Highway Administration, p. 433.