Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Quantification on Dam Condition Related to Internal Erosion of an Embankment Dam and its Applicability Evaluation

필댐의 내부침식과 관련된 댐 상태의 정량화 및 적용성 평가

  • Heo, Gun (Rural Research Institute, Korea Rural Community Cooperation) ;
  • Chung, Choong-Ki (Dept. of Civil and Environmental Engrg., Seoul National Univ.)
  • 허건 (한국농어촌공사 농어촌연구원) ;
  • 정충기 (서울대학교 건설환경공학부)
  • Received : 2018.10.15
  • Accepted : 2019.04.02
  • Published : 2019.04.30
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Abstract

The typical four conditions related to internal erosion were set from the results of the regular dam safety inspection for 17,500 dams, and a questionnaire survey was conducted for dam safety experts to quantify these four typical current dam conditions with scores between 0 and 10, respectively. In addition, we proposed 'possible score range' for each condition to minimize the decision limits for dam managers to quantify dam conditions while helping to quantify various dam conditions except 4 representative conditions. A case study based on 'quantified score' and 'possible score range' for each condition showed that this method consistently reflects the dangerousness of the dam and provides a reasonable probability of failure. This helps to overcome limitations of dam rating determination by weighted average, and it will help to evaluate dangerous dams as dangerous dams.

국내 농업용 댐 17,5000여개의 안전점검 결과를 바탕으로 필댐에 나타나는 내부침식(internal erosion)과 관련된 대표적인 4가지 상태를 설정하였다. 이들 상태들을 정량화하기 위하여 댐 안전관리 전문가를 대상으로 설문조사를 실시하고 각 상태들에 대한 정량화된 점수를 제시하였다. 또한 4가지 대표 상태 이외의 다양한 댐 상태의 정량화를 도와주면서 댐 관리자들의 댐 상태 정량화 결정에 제한을 최소화 하고자 각 상태별 '부여가능한 점수의 범위(possible score range)'를 제시하였다. 각 상태별 '정량화된 점수'와 '부여가능한 점수의 범위'를 바탕으로 Case Study를 실시하여 본 방법이 댐의 위험 정도를 일관성 있게 반영하고 합리적인 수준의 파괴확률 값을 제공함을 알 수 있었다. 이는 기존의 댐 안전관리 방법이 가지는 가중평균에 의한 댐 상태등급 결정의 한계점을 극복할 수 있게 도와주어 실제로 위험한 댐을 위험한 댐으로 인지할 수 있게 도와줄 것이다.

Keywords

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Fig. 1. Graph for plotting annual probability of failure vs. Current condition score (Heo and Chung, 2016)

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Fig. 2. Correlation Analysis for Verifying Consistency of Failure Probability Estimation Due to Internal Erosion

Table 1. Overall Failure Statistics for Large Embankment Dams (Modified based on Foster et al., 2000)

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Table 2. Questionnaire form

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Table 3. Results before removal of outliers

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Table 4. Results after removal of outliers

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Table 5. Results of possible score ranges

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Table 6. Case Study results for Consistency Verification

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Table 7. Comparison of the Safety rating of the downstream slope and Current dam condition score

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References

  1. Brown, A.J. and Gosden, J.D. (2004), "Interim Guide to Quantitative Risk Assessment for UK Reservoirs", pp35-43 and Appendix C, pp.124-126.
  2. Bureau of Reclamation and Corps of Engineers (2012), "Chapter 26: Internal Erosion", Best Practices in Dam and Levee Safety Risk Analysis. Draft, U.S. Bureau of Reclamation and Corps of Engineers, Denver, CO.
  3. Department for Environment Food and Rural Affairs (2013), "Guide to risk assessment for reservoir safety management", Volume 2.
  4. Foster, M., Fell, R., and Spannagle, M. (2000), "A Method for Assessing the Relative Likelihood of Failure of Embankment Dams by Piping", Canadian Geotechnical Journal, Vol.37, No.5, pp.1031-1033.
  5. Fell, R., Foster, M., Davidson, R., Cyganiewicz, J., Sills, G., and Vroman, N. (2008), "A Unified Method for Estimating Probabilities of Failure of Embankment Dams by Internal Erosion and Piping", URS Australia Pty Ltd. Sydney, Australia. [Prepared for the US Bureau of Reclamation]
  6. Heo, G. and Chung, C.K. (2016), "Quantification on the probability of dam failure due to internal erosion using event tree analysis", Proc., 84 th ICOLD Annual Meeting 2016, Johannesburg, S. Africa.
  7. Scott, G.A. (2011), "The Practical Application of Risk Assessment to Dam Safety", Georisk 2011, pp.129-168.