Journal of the Korean GEO-environmental Society (한국지반환경공학회 논문집)

Korean Geo-Environmental Society (한국지반환경공학회)
권호 표지

Estimating Groundwater Level Variation due to the Construction of a Large Borrow Site using MODFLOW Numerical Modeling

대규모 토취장 개발 예정 지역의 수치모델을 이용한 지하수위 변동 예측

  • Published : 2012.10.01
⟨ Previous Next ⟩

Abstract

A numerical model and field monitoring data are used to estimate a change in groundwater level at a borrow site, which will be constructed at the mountainous area with a large ground excavation in the study area, Hwaseong city. Lithologic data and hydraulic coefficients are collected at 9 boreholes and also groundwater levels are measured at these boreholes and existing wells in the study area. Additionally, groundwater recharge rate for the type of land cover is estimated using water budget analysis; 133.34mm/year for a mountainous area, 157.68mm/year for a farming area, 71.08mm/year for an urbanized area, and 26.06mm/year for a bedrock exposure area. The change in groundwater level in and around a borrow site is simulated with Modflow using these data. The result of a transient model indicates that a removal of high ground (over 40El.m) by an excavation will produce a decrease in groundwater levels, up to 1 m, around a borrow site in 10 years. It also explains that this ground excavation will bring about the decreases of 9.4% and 7.0% for groundwater recharge and surface runoff, respectively, which are the factors causing groundwater level's change. This study shows that it is required to construct the groundwater monitoring wells to observe the change of groundwater near a borrow site.

본 연구에서는 산지 지형에서 토취장을 개발할 경우 상부의 지반 굴착으로 인한 지하수계의 변화를 현장 계측자료와 모델링을 활용하여 예측하고자 하였다. 9개소의 시추조사를 통하여 지층 분포와 수리상수를 구하고 현장 지하수위 조사를 실시하였으며, 물수지 분석에 의한 지하수 함양량을 추정한 후 Modflow 프로그램에 적용함으로써 지하수위 변화를 예측하였다. 토취장 개발로 40 El.m 이상 지역이 제거될 경우를 가정하여 부정류 모델링을 수행한 결과, 토취장 최인접 지역에서 최대 1m 정도의 지하수위 강하가 나타나는 것으로 예측되었다. 또한, 절토로 인한 상부 지형의 제거는 9.4% 및 7.0%의 지하수 함양량과 지표 유출량의 감소를 초래하는 것으로 예측되었는데, 이는 지하수위 변화를 야기하는 요인으로 평가되었다. 향후 토취장 개발이 시작되면 이와 같은 지하수위 변화를 지속적으로 파악하기 위하여 지하수 관측정을 설치 운영할 필요가 있다.

Keywords

References

  1. Cho, S. I., Kim, C. S., Bae, D. S., Kim, K. S. and Song, M. Y.(2006), Analysis of a Groundwater Flow System in Fractured Rock Mass using the Concept of Hydraulic Compartment, The Journal of Engineering Geology, Vol. 16, No. 1, pp. 69-83.
  2. Chung, S. Y., Yoo, I. K., Yoon, M. J., Kweon, H. W. and Heo, S. H.(1999), Application of Geostatistical Methods to Groundwater Flow Analysis in a Heterogeneous Anisotropic Aquifer, The Journal of Engineering Geology, Vol. 9, No. 2, pp. 147-159.
  3. Dominico, P. A. and Schwartz, F. W.(1990), Physical and Chemical Hydrology, John Wiley and Sons, N.Y., pp. 75-77.
  4. Han, J. S. and Han, C.(1999), 3 Dimensional Groundwater Modelling and Application, Parkyoungsa, Seoul, pp. 181-182.
  5. Hoeksema, R .J., Clapp, R. B., Thomas, A. L., Hunley, A. E., Farrow, N. D. and Dearstone, K .C.(1989), Cokriging Model for Estimation of Water Table Elevation. Water Resources Research, Vol. 25, No. 3, pp. 429-438. https://doi.org/10.1029/WR025i003p00429
  6. Houlsby, A.(1976), Routine Interpretation of the Lugeon Water-test, Quarterly Journal of Engineering Geology, Vol. 9, pp. 303-313. https://doi.org/10.1144/GSL.QJEG.1976.009.04.03
  7. Kim, G. B., Son, Y. C. and Seo, K. S.(2010), Effect of Cut-off Wall Near the Entrance of Spillway Tunnel, The Journal of Engineering Geology, Vol. 20, No. 2, pp. 147-153.
  8. Lee, B. D., Choo, C. O., Lee, B. J., Cho, B. W., Hamm, S. Y. and Im, H. C.(2003), Numerical Modeling on the Prediction of Groundwater Recovery in the Youngchun Area, Kyungbook Province, Econ. Environ. Geol, Vol. 36, No. 6, pp. 431-440.
  9. Lee, J. H., Hamm, S. Y., Cheong, J. Y., Jeong, J. H., Park, S., Kim, N. H. and Kim, G. B.(2010), Numerical Simulation for Estimating Effects of Giheung Tunnel Construction on the Groundwater Flow System, The Journal of Engineering Geology, Vol. 20, No. 4, pp. 449-459.
  10. MOCT(Ministry of Construction and Transportation)(1996), National Master Plan for Groundwater, Seoul, pp. 87-113.
  11. Park, N. Y. and Kim, J. H.(1972), Geologic Map: Namyang 1:50,000, National Geological Survey, pp. 1-13.
  12. The Korean Society of Engineering Geology(2003), Investigation of Bedrock and Its Application, Seoul, pp. 1.6-1-1.6-125.
  13. Thornthwaite, C. W. and Mather, J. R.(1957), Instruction and Table for Computing Potential Evapotranspiration and the Water Balance, Laboratory of Climatology, Publication 10, Centerton, N.J., pp. 185-311.
  14. U. S. Department of the Interior (Bureau of Reclamation)(2001), Engineering Geology Field Manual, Volume II, Washington D.C., pp. 107-182.