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2018 Vol.34, Issue 7

Research Article

Estimation of Unconfined Compressive Strength (UCS) of Microfine Cement Grouted Sand

마이크로 시멘트로 그라우팅 된 모래의 일축압축강도 예측

Hongyeop Nam1
,
Woojin Lee2
,
Changho Lee3*
,
Hyunwook Choo4
남 홍엽1
,
이 우진2
,
이 창호3*
,
추 현욱4
1School of Civil, Environmental and Architectural Engrg., Korea Univ.
2School of Civil, Environmental Architectural Engrg., Korea Univ.
3Dept. of Marine and Civil Engrg., Chonnam National Univ.
4Dept. of Civil Engrg., Kyung hee Univ.
1고려대학교 건축사회환경공학부
2고려대학교 건축사회환경공학부
3전남대학교 해양토목학과 부교수
4경희대학교 사회기반시스템공학과 조교수
* Corresponding Author
31 July 2018. pp. 5-15
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Abstract

The unconfined compressive strength (UCS) test through coring is widely used to determine the reinforcement effect of the ground with grouting. However, the UCS test through coring can disturb the ground, is expensive and takes a lot of time to prepare the specimen. In this study, the factors affecting UCS of microfine cement grouted sand are evaluated and an empirical equation of UCS of microfine grouted sand is suggested. It is observed that UCS increases linearly until 28 days, however, the increasing rate of strength decreases sharply after that 28 days. The W/C ratio is dominant factor influencing UCS and UCS increases exponentially with the decrease of water/cement (W/C) ratio. Also, UCS increases linearly with increasing the relative density ranging from 30% to 70% and with decreasing median particle size. However, in case of W/C ratio=1 and K6 (D50=0.47 mm), UCS is lower than that of K4 (D50=1.08 mm) and K5 (D50=0.80 mm) due to filtration effect. Based on the experimental results, the empirical equation of UCS of microfine cement grouted sand can be expressed as the function of median particle size (D50), porosity (n) and W/C ratio.

Keywords
Microfine cement
Unconfined compressive strength (UCS)
Water/Cement ratio (W/C)
Relative density
Particle size

그라우팅을 통한 지반의 보강효과를 판단하기 위한 방법으로 코어링(coring)을 통한 일축 압축실험이 널리 실시되고 있는 실정이다. 하지만 코어링 시 원지반이 교란될 뿐만 아니라 시공비가 비싸며, 그라우팅 된 모래의 시편 준비에 많은 시간이 소요된다는 문제점이 있다. 따라서 본 연구에서는 마이크로 시멘트로 그라우팅 된 모래의 일축압축강도에 영향을 미치는 인자들을 비교/분석하고 28일 일축압축강도 추정식을 제안하였다. 마이크로 시멘트로 그라우팅 된 평균 입경이 서로 다른 인공 파쇄사(K4, K5 및 K6)의 일축압축강도는 양생기간 28일까지 선형적으로 증가하였으나 28일을 기점으로 강도의 증가율이 급격히 하락하였다. 물/시멘트(W/C) 비는 그라우팅 된 모래의 일축압축강도에 가장 큰 영향 인자이며, 일축압축강도는 W/C가 감소함에 따라 비선형적으로 증가하였다. 또한 일축압축강도는 상대밀도가 높아질수록 선형적으로 증가하였으며, 모래의 입자크기가 작아질수록 증가하는 경향을 보였으나 W/C=1, 및 K6(D50=0.47mm) 모래의 경우 필터레이션에 의하여 K4(D50=1.08mm)와 K5(D50=0.80mm) 모래의 일축압축강도보다 낮은 경향을 보였다. 실험결과를 바탕으로 마이크로 시멘트로 그라우팅 된 모래의 일축압축강도를 모래의 평균입경(D50), 간극률(n)과 물/시멘트(W/C) 비의 함수로 제안하였다.

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Information
  • Publisher :The Korean Geotechnical Society
  • Publisher(Ko) :한국지반공학회
  • Journal Title :Journal of the Korean Geotechnical Society
  • Journal Title(Ko) :한국지반공학회 논문집
  • Volume : 34
  • No :7
  • Pages :5-15
  • Received Date : 2018-03-28
  • Revised Date : 2018-06-19
  • Accepted Date : 2018-06-20
  • DOI :https://doi.org/10.7843/kgs.2018.34.7.5
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