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Research Article

Development and Application of Slime Meter for Evaluation of Slime Thickness in Borehole

굴착공 내 슬라임 두께 평가를 위한 슬라임미터의 개발 및 적용

Won-Taek Hong1
,
Gyuseong Woo2
,
Jong-Sub Lee3
,
Myung Jun Song4
,
Daesung Lim5
,
Min-Chul Park6*
홍 원택1
,
우 규성2
,
이 종섭3
,
송 명준4
,
임 대성5
,
박 민철6*
1Member, Postdoctoral Fellow, School of Civil, Environmental and Architectural Engrg., Korea Univ.
2Member, Assistant Junior Official, Daejeon Regional Office of Construction Management, Ministry of Land, Infrastructure and Transport
3Member, Prof., School of Civil, Environmental and Architectural Engrg., Korea Univ.
4Member, Pile Specialist, R&D Division, Hyundai Engrg. & Construction. Co., Ltd.
5Member, Senior General Manager, Research Team, Sambo E&C Co., Ltd.
6Member, Ph.D. Candidate, School of Civil, Environmental and Architectural Engrg., Korea Univ.
1정회원, 고려대학교 건축사회환경공학부 박사후연구원
2정회원, 국토교통부 대전지방국토관리청 주무관
3정회원, 고려대학교 건축사회환경공학부 교수
4정회원, 현대건설 연구개발본부 부장
5정회원, 삼보E&C 연구팀 선임부장
6정회원, 고려대학교 건축사회환경공학부 박사수료
* Corresponding Author
31 October 2018. pp. 29-38
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Abstract

The slime formed at the bottom of the borehole causes the excessive displacement and loss of the bearing capacity of the drilled shaft. In this study, the slime meter is developed for the evaluation of the slime based on the electrical properties of the fluid and the slime in the borehole. The slime meter is composed of a probe instrumented with electrodes and temperature sensor and a frame with rotary encoder, so that the slime meter profiles the electrical resistivity compensated with temperature effect along the depth. For the application of the slime meter, three field tests are conducted at a borehole with a diameter of 3 m and a depth of 46.9 m with different testing time and locations. For all the tests, the experimental results show that while electrical resistivities are constantly measured in the fluid, the electrical resistivities sharply increase at the surface of the slime. Therefore, the slime thicknesses are estimated by the differences in the depths of the slime surface and the ground excavation. The experimental results obtained at the same testing point with different testing time show that the estimated thickness of the slime increases by the elapsed time. Also, the estimated slime at the side of the borehole is thicker than that at the center of the borehole. As the slime meter estimates the slime in the borehole by measuring the electrical resistivity with simple equipment, the slime meter may be effectively used for the evaluation of the slime formed at the bottom of the borehole.

Keywords
Borehole
Drilled shaft
Electrical resistivity
Ground excavation
Slime

굴착공 저면에 형성된 슬라임은 현장타설말뚝의 과도한 침하 및 지지력 감소를 야기하므로 콘크리트 타설 전 해당 슬라임에 대한 조사가 요구된다. 본 연구에서는 굴착공 내 전기적 특성을 이용하여 굴착공 저면에 형성된 슬라임을 평가하기 위한 기법으로써 슬라임미터(slime meter)를 개발하였다. 슬라임미터는 전극 및 온도센서가 설치된 프로브 및 로터리엔코더가 설치된 프레임으로 구성되어 굴착공 심도에 따라 온도영향이 고려된 전기비저항을 평가할 수 있다. 슬라임미터의 적용을 위하여 직경 3m, 심도 46.9m의 굴착공에 대해 시험시간 및 위치가 서로 다른 총 3회의 현장실험이 수행되었다. 3회의 현장실험 모두 굴착공 내 유체에서 일정한 전기비저항이 측정되었으나 슬라임 표면이 존재하는 심도에서 전기비저항이 급격히 증가하는 결과를 보였으며, 해당 심도 및 지반 굴착심도의 차를 이용하여 슬라임의 두께를 산정할 수 있었다. 슬라임 두께 산정 결과, 동일 실험위치에서의 슬라임 두께는 시간 경과에 따라 증가하였으며 가장자리에서의 슬라임이 중앙부의 슬라임보다 두껍게 평가되었다. 본 연구에서 개발된 슬라임미터는 간소화된 장비구성으로 굴착공 내 전기비저항을 평가하여 슬라임 두께를 산정하므로 향후 굴착공 저면의 슬라임 평가를 위한 기법으로써 활용될 수 있을 것이라 기대된다.

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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 :10
  • Pages :29-38
  • Received Date : 2018-08-28
  • Revised Date : 2018-10-05
  • Accepted Date : 2018-10-08
  • DOI :https://doi.org/10.7843/kgs.2018.34.10.29
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