Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Estimation of Slime Thickness of Bored Piles by Using Borehole Electrical Resistivity Method

시추공 전기비저항 기법을 활용한 현장타설말뚝의 슬라임층 두께 평가

  • Chun, Ok-Hyun (School of Civil, Environmental, and Architectural Engineering, Korea University) ;
  • Lee, Jong-Sub (School of Civil, Environmental, and Architectural Engineering, Korea University) ;
  • Park, Min-Chul (Geotechnical Engineering Team, Backyoung) ;
  • Bae, Sung-Gyu (Department of Environment and Construction Management, Korea Air Line Co., Ltd.) ;
  • Yoon, Hyung-Koo (Department of Geotechnical Disaster Prevention Engineering, Daejeon University)
  • 전옥현 (고려대학교 건축사회환경공학부) ;
  • 이종섭 (고려대학교 건축사회환경공학부) ;
  • 박민철 (백경 GNC) ;
  • 배성규 (대한항공 환경건설관리부) ;
  • 윤형구 (대전대학교 지반방재공학과)
  • Received : 2013.01.22
  • Accepted : 2013.03.18
  • Published : 2013.03.29
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Abstract

The slime, deposited in the bored pile due to falling soil particle, reduces the bearing capacity of bored pile and thus the stability of construction also decreases. The weight pendulum and iron have been used for estimating the slime thickness based on the subjective judgment and thus the previous method has a limitation of reliability. The objective of this paper is to suggest the method for estimating the slime thickness by using characteristics of electrical resistivity as scientific method. The temperature-compensation resistivity probe (TRP), which has a conical shape and the diameter of 35.7mm, is applied to the measurement of the electrical resistivity in the borehole during penetration. The field tests are carried out for estimating the slime thickness in the application site of bored pile. The slime thickness is calculated through the difference between excavation depth of borehole and measured data. Furthermore, the laboratory tests are also conducted for investigating effects of casing, time elapsing and relative density by using the specimen of slime. The laboratory test supporting the suggested method is reasonable for determining the slime depth. The paper suggests that the electrical resistivity method may be a useful method for detecting slime thickness and the method is expected to be applicable to various sites of bored piles.

말뚝 시공 시 선단 부분에 쌓이는 슬라임은 현장타설말뚝의 선단지지력을 감소시켜 구조물의 안정성에 큰 영향을 미친다. 슬라임의 존재 유무는 주로 다짐추 혹은 철근을 낙하시켜 판정하고 있으며, 이와 같은 방법은 주관적인 판단결과로 신뢰성에 한계가 있다. 본 논문에서는 물리탐사기법 중 하나인 전기비저항 특성을 활용하여 슬라임층의 존재 여부와 두께를 과학적이고 객관적으로 평가하는 방법을 제시하고자 한다. 슬라임층의 전기비저항 특성을 평가하기 위하여 기존에 개발된 온도보상형 전기비저항 프로브(TRP)를 활용하였으며, TRP의 형상은 원뿔형태로 직경은 표준콘 관입실험 장비와 동일하게 35.7mm이다. 현장타설말뚝 공법 중 P.R.D(Percusion Rotary Drill) 방법을 적용하고 있는 현장에서 실험을 수행하였으며 전기비저항의 결과를 이용하여 슬라임층의 두께를 평가하였다. 신뢰성 높은 분석을 도모하고자 현장 슬라임층을 이용하여 케이싱 효과, 시간경과 그리고 상대밀도에 따른 실내 실험도 추가적으로 수행하였다. 본 연구에서는 전기비저항을 이용하여 슬라임층 두께를 산정하는 방법이 합리적임을 보여주며, 추후 다양한 지층과 말뚝 시공 공법에 적용성이 기대된다.

Keywords

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