DOI QR코드

DOI QR Code

강우특성을 고려한 불포화 잔적토 비탈면의 붕괴사례 연구

Case Study on the Instability of the Slopes in Unsaturated Residual Soils Considering the Rainfall Characteristics

  • 투고 : 2014.09.29
  • 심사 : 2014.11.03
  • 발행 : 2015.01.01

초록

본 연구에서는 불포화토에 대한 압력판 추출시험을 수행하여 함수특성곡선을 구하고 불포화토의 삼축압축시험을 실시한 후, Geostudio 2007의 SEEP/W 해석 프로그램을 이용하여 부정류 침투해석을 수행하였으며, SLOPE/W 해석프로그램으로 비탈면 안정성을 검토하였다. 그 결과 모관흡수력 증가에 따라 순체적응력과 축차응력이 증가하고 겉보기점착력도 선형적으로 증가함으로 써 전단강도가 증가함을 알 수 있었다. 강우침투해석 결과 높은 음의 간극수압에서는 적은 강우량에도 간극수압의 증가폭이 크게 나타났고, 일정깊이 이하의 심도에서 지하수위의 상승을 제외하면 강우의 영향을 받지 않음을 알 수 있었다. 비탈면의 파괴양상과 동일한 단면으로 파괴면을 일정하게 고정시켜 안정 해석한 결과 실제로 비탈면 파괴 시에 안전율이 1.0 이하로 낮아지는 것을 확인할 수 있었다.

This study has obtained Soil Water Retention Curve (SWRC) of the unsaturated soil from the volumetric pressure plate extractor test and the triaxial compression tests was also conducted. By using the rainfall data measured in the site the seepage analysis of unsteady flow was performed with the program of SEEP/W in Geostudio 2007 and stability of the slope was analyzed with SLOPE/W program. Results of analyses show that shear strength of the unsaturated soil increases with the increase of matric suction. And it was also found that the net volumetric stress and the apparent cohesion increased with the matric suction. The seepage analysis of rainfall represents that the increasing rate of negative pore pressure at the zone of large negative pore pressure is appeared to be high even though lower rainfall intensity, but this tendency declines with ground depth. The stability analysis of slope was carried out for the actual plane of failure with the data representing the field condition. The factor of safety thus calculated was about unity (1.0) or just below, which means that the adopted method of analysis is in good agreement with the field condition.

키워드

참고문헌

  1. Bishop, A. W. and Blight, G. E. (1963), Some aspects of effective stress in saturated and unsaturated soils, Geotechnique, Vol. 13, No. 3, pp. 177-197. https://doi.org/10.1680/geot.1963.13.3.177
  2. Fredlund, D. G., Morgenstern, N. R. and Widger, R. A. (1978), The shear strength of unsaturated soil, Canadian Geotechnical Journal, Vol. 15, No. 3, pp. 313-321. https://doi.org/10.1139/t78-029
  3. Korea Infrastructure Safety Corporation (2011), Design guide on engineered slopes, pp. 31-33 (in Korean).
  4. Lee, Y. H., Oh, S. B. and Park, Y. M. (2013), Development of evaluation technique of a slope stability of residual soils decomposed of sedimentary rocks in Daegu-Gyeongbuk region considering unsaturated behavior characteristics, Korea Agency for Infrastructure Technology Advancement, pp. 14-18 (in Korean).
  5. Lu, N. and Likos, W. J. (2006), Suction stress characteristic curve for unsaturated soils, Jounal of Geo-technical and Geoenvironmental Engineering, Vol. 132, No. 2, pp. 131-142. https://doi.org/10.1061/(ASCE)1090-0241(2006)132:2(131)
  6. Lu, N., Godt, J .W. and Wu, D. T. (2010), A closed-form equation for effective stress in unsaturated soils, Water Resources Research, Vol. 46, doi:10. 1029/ 2009 WR008646, pp. 1-14 https://doi.org/10.1029/2009WR008646
  7. Mualem, Y. (1976), A new model for predicting the hydraulic conductivity of unsaturated porous media, Water Resources Research, Vol. 12, No. 3, pp. 593-622.
  8. Oh, S. B., Lu, N., Kim, Y. K., Lee, S. J. and Lee, S. R. (2012), Relation between the soil-water characteristic curve and the suction stress characteristic curve: Experimental evidence from tests on residual soils, Journal of Geotechnical and Geoenvironmental Engineering, Vol. 138, No. 1, pp. 47-57. https://doi.org/10.1061/(ASCE)GT.1943-5606.0000564
  9. van Genuchten, M. T., (1980), A Closed-form equation for predicting the hydraulic conductivity of unsaturated soils, Soil Science Society of America Journal, Vol. 44, No. 5, pp. 892-898. https://doi.org/10.2136/sssaj1980.03615995004400050002x
  10. Vanapalli, S. K., Fredlund, D. G., Pufahl, D. E. and Clifton, A. W. (1996), Model for the prediction of shear strength with respect to soil suction, Canadian Geotechnical Journal, Vol. 33, No. 3, pp. 379-392. https://doi.org/10.1139/t96-060