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

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

DOI QR Code

Study on Correlation between Dynamic Cone Resistance and Shear Strength for Frozen Sand-Silt Mixtures under Low Confining Stress

낮은 구속응력에서 모래-실트 혼합토의 동결강도 평가를 위한 동적 콘 저항력 및 전단강도 상관성 연구

  • Kim, Sangyeob (School of Civil, Environmental and Architectural Engineering, Korea University) ;
  • Lee, Jong-Sub (School of Civil, Environmental and Architectural Engineering, Korea University) ;
  • Hong, Seungseo (Korea Institute of Construction Technology) ;
  • Byun, Yong-Hoon (School of Civil, Environmental and Architectural Engineering, Korea University)
  • Received : 2015.07.18
  • Accepted : 2015.11.24
  • Published : 2016.01.01
Download PDF
⟨ Previous Next ⟩

Abstract

Investigation of in-situ ground in cold region is difficult due to low accessibility and environmental factors. In this study, correlation between dynamic cone resistance and shear strength is suggested to estimate the strength of frozen soils by using instrumented dynamic cone penetrometer. Tests were conducted in freezing chamber after preparing sand-silt mixture with 2.3% water content. Vertical stresses of 5 kPa and 10 kPa were applied during freezing, shearing, and penetration phase to compare the dynamic cone resistance and shear strength. The dynamic cone resistance, additionally, is calculated to minimize the effect of energy loss during hammer impact. Experimental results show that as the shear strength increases, the dynamic cone penetration index (DCPI) decreases nonlinearly, while the dynamic cone resistance increases linearly. This study provides the useful correlation to evaluate strength properties of the frozen soils from the dynamic cone penetration and direct shear tests.

극한지에서는 환경적 요인과 접근성의 한계에 따라, 동결토의 강도를 현장 상태에서 파악하기 어렵다. 본 연구에서는 극한지 현장의 동결강도를 평가하기 위하여 계장화된 동적 콘 관입기로부터 산정된 동적 콘 저항력과 직접전단실험으로부터 획득된 전단강도 간의 상관성을 조사하였다. 실트가 혼합된 주문진사를 함수비 2.3%로 동일하게 조성하였으며, 시료를 냉동 챔버 내에서 동결시킨 후 직접전단실험과 동적 콘 관입실험을 진행하였다. 실험은 동결과정 및 전단과정, 그리고 동적 콘 관입과정에서 수직응력을 5kPa 및 10kPa로 조합한 4가지 경우로 구성하였으며 이에 따른 동적 콘 관입지수와 전단강도를 산정하였다. 또한 해머타격으로부터 전달되는 에너지의 손실에 대한 영향을 최소화하기 위하여 선단에서 산정된 에너지 및 변위를 이용함으로써 동적 콘 저항력을 산출하였다. 직접전단실험 및 동적 콘 관입실험을 수행한 결과 구속조건에 의한 전단강도의 증가에 따라 동적 콘 관입지수는 비선형적으로 감소하였으며, 동적 콘 저항력은 전단강도와 선형적으로 비례하는 관계로 나타났다. 본 연구는 동결토에 대한 동적 콘 관입실험과 직접전단실험을 통한 강도정수를 비교 및 평가한 연구이며 본 연구에서 도입된 동적 콘 저항력은 극한지 현장에서 동결토의 강도를 추정하기 위한 유용한 지표가 될 수 있을 것으로 기대된다.

Keywords

References

  1. Byun, Y. H. and Lee, J. S. (2013), Instrumented dynamic cone penetrometer corrected with transferred energy into a cone tip: a laboratory study, Geotechnical Testing Journal, Vol. 36, No. 4, pp. 533-542. https://doi.org/10.1520/GTJ20120115
  2. Byun, Y. H., Yoon, H. K., Kim, Y. S., Hong, S. S. and Lee, J. S. (2014), Active layer characterization by instrumented dynamic cone penetrometer in Ny-Alesund, Svalbard, Cold Regions Science and Technology, Vol. 104-105, pp. 45-53. https://doi.org/10.1016/j.coldregions.2014.04.003
  3. Christ, M. and Park, J. B. (2010), Laboratory determination of strength properties of frozen rubber-sand mixtures, Cold Regions Science and Technology, Vol. 60, pp. 169-175. https://doi.org/10.1016/j.coldregions.2009.08.013
  4. Da Re, G., Germaine, J. and Ladd, C. (2003), Triaxial testing of frozen sand: equipment and examples results, Journal of Cold Regions Engineering, Vol. 17, No. 3, pp. 90-118. https://doi.org/10.1061/(ASCE)0887-381X(2003)17:3(90)
  5. Kang, J. M., Lee, J. G., Lee, J. Y. and Kim, Y. S. (2013), Analysis of the relationship between unconfined compression strength and shear strength of frozen soils, Journal of Korean Geosynthetics Society, Vol. 12, No. 3, pp. 23-29 (in Korean). https://doi.org/10.12814/jkgss.2013.12.3.023
  6. Kim, S. Y., Lee, J. S., Kim, Y. S. and Byun, Y. H. (2015), Evaluation of the shear strength and stiffness of frozen soil with a low water content, The Journal of Engineering Geology, Vol. 25, No. 1, pp. 93-102 (in Korean). https://doi.org/10.9720/kseg.2015.1.93
  7. Lee, J. Y. and Choi, C. H. (2012), A study for shear strength characteristics of frozen soils under various temperature conditions and vertical confining pressures, Journal of the Korean Geo-Environmental Society, Vol. 13, No. 11, pp. 51-60 (in Korean).
  8. Mohammadi, M. M. and Robertson, P. K. (2008), A numerical study of chamber size and boundary effects on cpt tip resistance in NC sand, Scientia Iranica, Vol. 15, No. 5, pp. 541-553.
  9. Mohammadi, S. D., Nikoudel, M. R., Rahimi, H. and Khamehchiyan, M. (2008), Application of the dynamic cone penetrometer(DCP) for determination of the engineering parameters of sandy soils, Engineering Geology, Vol. 101, No. 3-4, pp. 195-203. https://doi.org/10.1016/j.enggeo.2008.05.006
  10. Odebrecht, E., Schnaid, F., Rocha, M. M. and Bernardes, G. P. (2005), Energy efficiency for standard penetration test, Journal of Geotechnical and Geoenvironmental Engineering, Vol. 131, No. 10, pp. 1252-1263. https://doi.org/10.1061/(ASCE)1090-0241(2005)131:10(1252)
  11. Yasufuku, N., Springman, S. M., Arenson L.U. and Ramholt, T. (2003), Stress-dilatancy behavior of frozen sand in direct shear, Proc. Of the Eighth International Conference on Permafrost, Switzerland, pp. 1253-1258.
  12. Zhu, Y. and Carbee, D. L. (1984), Uniaxial compressive strength of frozen silt under constant deformation rates, Cold Regions Science and Technology, Vol. 9, No. 1, pp. 3-15. https://doi.org/10.1016/0165-232X(84)90043-0