Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Experimental Study on the Effect of Drilling Fluid with Different Mix Designs for Bore Hole Collapse Prevention

시추 안정액 배합설계에 따른 공벽 붕괴방지 효과에 관한 실험적 연구

  • 유충식 (성균관대학교 건축토목공학과) ;
  • 최정혁 (성균관대학교 건설환경시스템공학과) ;
  • 한윤수 (현대중공업(주))
  • Received : 2014.10.14
  • Accepted : 2015.01.08
  • Published : 2015.01.31
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Abstract

This paper presents the results of a reduced-scale physical model investigation into the effect of drilling fluid with different mix designs for bore hole collapse prevention. The bore hole collapse prevention mechanism for the bentonite based drilling fluid was first discussed together with the effect of conditioning with different additives on engineering characteristics of bentonite based drilling fluid. Reduced-scale model tests were then carried out considering field procedures for cases with a decomposed granitic soil with 20% fines and a sand with various drilling fluids with different mix designs. The results indicated that the addition of polymer to the bentonite based drilling fluid decreases the amount of drilling fluid injected, the drilling fluid infiltration thickness and increases the final depth of excavation. Also revealed is that the effect of polymer on the performance of drilling fluid is more pronounced in the decomposed granite soil with 20% fines than the sand. Practical implications of the findings from this study are discussed in great detail.

본 논문에서는 지반 시추시 공벽붕괴 방지를 위해 적용되는 시추 안정액(drilling fluid)의 다양한 배합설계에 따른 공벽붕괴 방지 효과에 대한 실험적 연구 결과를 다루었다. 이를 위해 먼저 벤토나이트 계열 안정액의 공벽 붕괴 방지 메카니즘을 검토하였으며 아울러 벤토나이트계 안정액의 배합(conditioning)에 따른 안정액의 성능지표 변화에 대한 실험결과를 간략히 기술하였다. 또한 지반시추(굴착) 및 안정액 투입을 간략히 모사하는 토조 장치를 구축하여 세립분이 20% 포함된 화강풍화토 및 모래지반을 대상으로 다양한 배합으로 조성된 벤토나이트계 안정액에 대한 실험을 수행하고 안정액 투입량, 수평 침투범위, 굴착가능 깊이 등을 측정하여 공벽붕괴 방지 효과를 고찰하였다. 그 결과 벤토나이트에 폴리머를 추가할 경우 안정액 투입량 및 수평 침투범위가 굴착가능 깊이가 증가하는 것으로 나타났으며 폴리머의 공벽유지 기능 향상 정도는 모래층보다 화강풍화토 지반에서 보다 뚜렷하게 발휘되는 것으로 검토되었다. 본 논문에서는 도출된 연구결과가 실무적 차원에서 지니는 의미에 대한 내용을 기술하였다.

Keywords

References

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