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Applicability of Preconsolidation Pressure Interpretations of Korean Marine Clays

국내 해성점토 지반에 대한 선행압밀압력 평가방법의 적용성

Sang-Guk Jeong1*
정 상국1*
1Member, Professor, Department of Civil Engineering, Songwon University
*교신저자. *Corresponding Author. 
30 December 2017. pp. 93-101
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Abstract

In this study, a subjective weighting factors were awarded based on some indication of the difficulty of assessing the preconsolidation stress using traditional methods (Casagrande, Onitsuka et al., Silva, Becker et al., Janbu and Karlsrud methods) such as those proposed by Casagrande and Janbu using undisturbed sample obtained from Gwangyang dredged clay with high plasticity located in the southern area of Korean peninsular. These numbers only assess the relative ease of finding preconsolidation stress and say nothing regarding the accuracy of the value. The data were compared with measurements of undrained shear strength using strength incremental ratio, checking where or not the values are in the range of 0.25 to 0.35 (typical values of Korean marine clay) and analyzing standard deviation(degree of variability). The measurements of undrained shear strength were obtained from unconfined compression tests (UCT). When determining preconsolidation stress of Korean marine clay, at first, the work method proposed by Becker et al. and the bilogarithmic method proposed by Onitsuka et al. should be used. In addition, preconsolidation pressure should be estimated using the traditional Casagrande method as a basic of comparison.

Keywords
Preconsolidation stress
Weighting factor
Strength incremental ratio
Dredged clay

본 연구에서는 고소성 점토지반으로 구성된 광양지역의 준설매립층 및 원지반층에서 채취된 자연 시료를 이용하여 기존에 제안된 6가지 방법(Casagrande, Onitsuka, Silva, Becker, Janbu, Karlsrud)으로 선행압밀압력을 산정하는데 있어서 상대적인 용이성을 기준으로 5등급의 가중치 점수를 부여 하였다. 이 때, 높은 등급이 부여된다는 것이 곧바로 정확한 선행압밀압력의 산정을 의미하는 것은 아니므로, 불교란 시료에 의한 일축압축강도를 구한 후 압밀압력과의 상관관계를 나타내는 강도증가율 을 평가하였다. 이를 토대로, 각각의 방법으로 평가된 선행압밀압력과 비배수전단강도의 비, 즉, 강도증가율이 국내 해성 점성 토 지반의 일반적인 값의 범위인 0.25∼0.35 사이의 분포 유무 및 표준편차(강도증가율의 변화폭)를 분석하여 적용성을 평가하 였다. 그 결과, Becker 및 Onitsuka 방법의 평균 가중치가 다른 방법들(Casagrande, Janbu, Karlsrud)에 비해 낮고 강도증가율도 국내 해성점토 지반의 일반적인 값의 범위에 있으며, 표준편차도 낮게 평가되어 일관성 있는 평가가 가능한 것으로 분석되었다.

References
1
Becker, D. B., Crooks, J. H. A., Been, K. and Jefferies, M. G. (1987), “Work as a criterion for determining in situ and yield stresses in clays”, Canadian Geotechnical Journal, Vol. 24, pp. 549-564.
2
Becker, D. B., Crooks, J. H. A., Benn, K., and Jefferies, M. G. (1988), “Work as a criterion for determining in situ and yield stresses in clays: Reply”, Canadian Geotechnical Journal, Vol.25, No.4, pp.848-850.
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Clementino, R. V. (2005), “Discussion: An oedometer test study on the preconsolidation stress of glaciomarine clays”, Canadian Geotechnical Journal, Vol.42, No.3, pp.972-974.
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Information
  • Publisher :Korean Geosythetics Society
  • Publisher(Ko) :한국지반신소재학회
  • Journal Title :Journal of the Korean Geosynthetics Society
  • Journal Title(Ko) :한국지반신소재학회 논문집
  • Volume : 16
  • No :4
  • Pages :93-101
  • Received Date : 2017-11-10
  • Revised Date : 2017-11-04
  • Accepted Date : 2017-12-05
  • DOI :https://doi.org/10.12814/jkgss.2017.16.4.093
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