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26 June 2012

Investigation on final closing section of sea dike. 26 June 2012. Gun Heo. Korea Rural Research Institute. Contents. I. Introduction. II. In-situ Experiments. - Borehole Image Processing System (BIPS). - In-Situ permeability test. III. Piezometer Installation. IV.

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26 June 2012

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  1. Investigation on final closing section of sea dike 26 June 2012 Gun Heo Korea Rural Research Institute

  2. Contents I Introduction II In-situ Experiments - Borehole Image Processing System (BIPS) - In-Situ permeability test III Piezometer Installation IV Results and Discussion V Conclusions

  3. Background & Purpose Construction Condition of the Final Closing Section Purpose of Seadike were Concerned • Seawater Blocking • Securing fresh water • Development Internal • Piping andErosion Embankment • Desalination delay due to • excessive infiltration • The riprap-bottom layer connects both • seaside and lakeside, so permeable • Reclaimed with dredged sands Dredged Sands Riprap Bottom Layer Determine whether need reinforcement Effective Safety management seadike Evaluate the status of riprap layer Establish a long-term monitoring plan

  4. Outline Installation Piezometer Permeation Filling Status Items To evaluate the Permeation To measure the Pore Pressure To evaluate the Filling Status Purpose Installation Piezometers and Building Monitoring System (Automated) Borehole Image Processing System (BIPS) Detailed Task In-situ Permeability test Comparison the degree of permeability (General / Final closing) Long-term Monitoring ⇒ Evaluate the temporal variation of Filling Status ⇒Propose Criteria for Monitoring Visually check the Filling Status of the Bottom Layer. Utilization • Determine whether need reinforcement • Safety Management • Evaluated Current state of the filling • & temporal variation of Filling Status • Proposed Criteria for Monitoring Field test results + Data measured

  5. To find the most vulnerable sections… Bottom Protection Layer of the Final Closing Section < General Section > < Final Closing SectionL = 1.8 km > < General Section>

  6. Electrical Resistivity Results Above No. 60+25 Relatively low resistivity and showing the continuity sections Below electrical resistivity results of No. 59+60~No. 62+35(5m electrode gap)

  7. Selected Sections(3 Final Closing Sections, 1 GeneralSection) <General> No. 82 + 00 <Final Closing> No. 65 + 00 <Final Closing> No. 69 + 80 <Final Closing> No. 60 + 25

  8. BIPS (Borehole Image Processing System) Results BIPS •Top (13.9m) •Dredged Sands •Riprap •Riprap • Dredged Sands • Bottom (17.1m) • To decipher the filling degree of the bottom layer

  9. In-situ Permeability test Permeability Test Results To compare the differences in permeability coefficients Casing <Embankment/Bottom Layer> <General/Final Closing> The differences are not significant

  10. Installation Piezometers Piezometer Cross-Sectional Location Items I General Section 3 Final Sections Piezometer • Automated measurement system has been built for four-sections • By measuring the pore pressure, • Compare those between general section and Final closing sections, evaluate the filling status of the bottom layer • In addition, by conducting long-term monitoring , evaluate the safety of seadike with hydraulic head loss ratio • Arranged piezometers to compare the pore pressure of each section • (between the final closing section and normal section) • Arranged piezometers to compare the pore pressure of each point • (between P1 and P3, P3 and P7) • 4 piezometers in bottom protection layer (P-1,3,5,7) • 4 piezometers in embankment (P-2,4,6,8) 10

  11. Menu Bar 상단 메뉴 Floor plan 방조제 평면도 Measured Value 범례 및 계측요약 최근 계측데이터 실시간 표시 Cross-section 계측 단면도 Legend 경고 표출범례 Pore pressure Hydraulic Head Loss Ratio 간극수압그래프 수두손실율 그래프 Monitoring Program

  12. Measurement ResultsNo.60+25(Final Closing section) P3 P1 Pore Pressure(kg/cm2) Pore Pressure(kg/cm2) Time(day) Time(day) P7 P5 Pore Pressure(kg/cm2) Pore Pressure(kg/cm2) Time(day) Time(day) • Pore pressure changes due to tidal fluctuations that are quite stable • From sea side to the lake side, the changes in pore pressure gradually decreases

  13. Measurement ResultsNo.65+00(Final Closing section) P3 P1 Pore Pressure(kg/cm2) Pore Pressure(kg/cm2) Time(day) Time(day) P7 P5 Pore Pressure(kg/cm2) Pore Pressure(kg/cm2) Time(day) Time(day) • Pore pressure changes due to tidal fluctuations that are stable • From the sea side to the lake side, the changes in pore pressure gradually decreases

  14. Measurement ResultsNo.69+80(Final Closing section) P3 P1 Pore Pressure(kg/cm2) Pore Pressure(kg/cm2) Time(day) Time(day) P7 P5 Pore Pressure(kg/cm2) Pore Pressure(kg/cm2) Time(day) Time(day) • Pore pressure changes due to tidal fluctuations that are stable • From the sea side to the lake side, the changes in pore pressure gradually decreases

  15. Measurement ResultsNo.82+00(General section) P3 P1 Pore Pressure(kg/cm2) Pore Pressure(kg/cm2) Time(day) Time(day) P7 P5 Pore Pressure(kg/cm2) Pore Pressure(kg/cm2) Time(day) Time(day) • Pore pressure changes due to tidal fluctuations that are stable • From the sea side to the lake side, the changes in pore pressure gradually decreases • General section shows a smaller value than final closing section.

  16. Building Monitoring System • Installation Piezometer • - 3 on the final closing sections(No.60+25, No.65+00, No.69+80) • - 1 on the general section(No.82+00) • - 8 Piezometers are installed on each section • Monitoring Program • - Express the results and Monitor for long-term Summary • Every piezometer is operating properly • Reliable pore pressure data are being collected • Sea-side : Large Fluctuation, Lake-side : Small Fluctuation

  17. Hydraulic Head Loss Ratio Hydraulic Head Loss Ratio Hydraulic Head Loss Ratio Tide/Pore pressure Head Tide (m) Pore pressure head (m) Sea-side embankment inner-side • a : Hydraulic Head Loss Ratio • ΔHp1,2 : changes of pore pressure head at P1, P2 • “a” has the value of 0~1 • when a=0, ΔHp1 = ΔHp2, • a=1, ΔHp2 = 0 ← NOT affected by tide at all Criteria(?) Time (day) • Overlapped two graphs. • Gray : tide level • Black : Pore pressure Head of somewhere inside the structure which is affected by tide • but, depends on the position and the time, the ranges of pore pressure will be changed • Hard to set a criteria • The value of 0~1 • Closer to 0, Unstable • Closer to 1, stable P1-P2 EL(m) R2=Coefficient of determination P1=tide level EL(m)

  18. Hydraulic Head Loss Ratio Changes of Trends Upward (Enlarged Head Difference) Downward (Lessened Head Difference) degree of dispersion (Change of the Infiltration Path) Changes of inclination

  19. With the Hydraulic Head Loss Ratio Evaluation by Hydraulic Head Loss Ratio(No.60+25) Bottom Protection Layer Embankment a a R2 R2 • At P1, a = 0.228 R2= 0.931, Blocking the water looks worse, but the behavior is stable • At P7, a = 0.972 R2= 0.997 Closer to the Lake-side, values getting higher • At P2, a = 0.289 R2= 0.935, Blocking the water looks worse, but the behavior is stable • At P8, a = 0.972 R2= 0.993 Closer to Lake-side, a value becomes higher

  20. Evaluation by Hydraulic Head Loss Ratio(No.65+00) Bottom Protection Layer Embankment a a R2 R2 • At P2, a = 0.508 R2= 0.974, Blocking the water looks worse, but the behavior is stable • At P8, a = 0.961 R2= 0.998 Closer to Lake-side, a value becomes higher • At P1, a = 0.312 R2= 0.950, Blocking the water looks worse, but the behavior is stable • At P7, a = 0.917 R2= 0.997 Closer to Lake-side, a value becomes higher

  21. Evaluation by Hydraulic Head Loss Ratio(No.69+80) Bottom Protection Layer Embankment a a R2 R2 • At P1, a = 0.203 R2= 0.873 Closer to sea-side, Blocking the water looks worse, but the behavior is stable • At P7, a = 0.855 R2= 0.991 Closer to Lake-side, a value becomes higher • At P2, a = 0.267 R2= 0.867 Closer to sea-side, Blocking the water looks worse, but the behavior is stable • At P8, a = 0.957 R2= 0.997 Closer to Lake-side, a value becomes higher

  22. Evaluation by Hydraulic Head Loss Ratio(No.82+00) Bottom Protection Layer Embankment a a R2 R2 • At P1, a = 0.295 R2= 0.937 Closer to sea-side, Blocking the water looks worse, but the behavior is stable • At P7, a = 0.979 R2= 0.997 Closer to Lake-side, a value becomes higher • At P2, a = 0.671 R2=0.993 • Even though it closes to sea-side “a” value is relatively higher than the Final closing section’s • At P8, a = 0.984 R2= 0.999 Closer to Lake-side, a value becomes higher

  23. Summary - Sea-side (P-1,3) : Blocking the water looks Bad, but the behavior is stable - Lake-side(P-5,7) : Blocking the water looks Good, and the behavior is stable - Blocking the water of the general section is Good, but the final closing sections also show a stable behavior -Reinforcement does not require now at the final closing section, however, need to monitor constantly

  24. Criteria suitable for long-term Monitoring Criteria(Ⅰ) Statistical Methods • Three times the standard deviation • were set to the criteria • By setting the criteria, • we could measure • - Abnormal data • - Upward mobility of trend lines • - Downward mobility of trend lines • - Changes of trend line inclination • After long-term monitoring, we will • - Review the adequacy of 3σ • as criteria • - Set the check-list in case of • odd behavior Criteria (+3σ) P1-P2 (m) Criteria (-3σ) Tide(m) Regressionand 3-sigma Graph

  25. Examples of setting Criteria(Ⅰ) No.60+25 P3 P1 P7 P5

  26. Criteria(Ⅱ) Criteria based on the change of Hydraulic Head Loss Ratio

  27. Criteria(Ⅱ) Criteria based on the change of Hydraulic Head Loss Ratio • By plotting the daily values, • can predict changes of hydraulic • head loss ratio • Suitable for • long-term monitoring Hydraulic Head Loss Ratio

  28. Conclusions Section Select • 3 on the Final Closing Section (No. 60+25, No. 65+00, No. 69+80) • 1 on the General Section (No. 82+00) In-situ Experiments • BIPS • : The gap was deemed to have been filled with the dredged sands • In-situ permeability test: comparison of the permeability coefficient • - Bottom protection layer / Embankment • - General / Final Closing Section • Difference is not large

  29. Building the Monitoring System • Every piezometer is operating properly • Evaluated the infiltration charcteristic by Hydraulic Head Loss Ratio • - Sea-side (P-1,3) • : Blocking the water looks Bad, but the behavior is stable • - Lake-side(P-5,7) • : Blocking the water looks Good, and the behavior is stable • untilnow, evaluated need not reinforcement, • but we will follow up the trend • Suggested 2 Methods for Long-term Monitoring • - Criteria Based on Statistical Method • (Review the adequacy of 3σ by long-term monitoring) • - Criteria based on the change of Hydraulic Head Loss Ratio • (By the regression equation of trend line)

  30. Applications • Verify the stability of the sea-dike of the final closing section • Monitoring technology for seawater intrusion were secured • Methods for the structures affected by the tide were presented

  31. Thank you very much!!

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