Stability Analysis of Flood Bunds, A study on Geotechnical Health Evaluation of Embankments

2. Stability Analysis of Flood Bunds, A study on Geotechnical Health Evaluation of Embankments Primary Author (Presenter) SUMAYYA NOSHIN SDO Irrigation Department Punjab Co Author MEHTAB ALAM Graduate Student , Chinese Academy of Sciences, China 1stInternational conference on advancing in engineering and technology (ICAET-2018)

3. Research Background Research Objectives Research Methodology Literature review NumiricalAnalysis Conclusions Recommendations

4. Flood constitutes one of the world’s most serious environmental hazards. Flood bunds or levees are the earthen hydraulic structures which are constructed along the rivers to control the flood water to avoid damages to the infrastructures and populations. L M B Breach of Tounsa Barrage (2010) Investigations were conducted under the supervision of Dr. Khalid Faroq.

5. Punjab has been the worst-hit province due to rains and floods, where more than 1.7 million of the population is affected. According to the NDMA, nearly 17,000 houses have been fully destroyed. Over 1,900 schools across the province were also damaged and remained non-operational

6. The traditional method of preventing flooding has long been to construct flood bunds adjacent to the river. • A weak embankment near any city area is a constant source of threat to that area. • Proper geotechnical evaluations and design is vital for proper functioning of such structures. • It is very essential to perform accurate geotechnical evaluation using modern geotechnical design techniques to check the stability and performance of such structures against the critical flood situations.

7. Research Objectives • To conduct geotechnical investigations of the Flood Bunds and evaluate geotechnical parameters for various analyses. • To perform geotechnical analyses including seepage analysis and slope stability analysis by modeling the bund structure in software (Geo-Studio) by incorporating the geotechnical parameters. • To compare the results of the analyses with the current empirical practice for analysis and design of the bund structure.

8. Research Methodology Literature Review and Data Collection Selection of Flood Bunds for study and Desk study of selected sites Performance of Site Investigations and collection of Soil Samples Performance of Lab Tests on Selected Soil Samples Selection / Evaluation of soil parameters Modeling of selected flood bunds in Geo-Studio Calculation of River Embankment Breaching Vulnerability Index Conclusions and Recommendations

9. Bhanbhro et al. (2014) studied Failures in embankments of Irrigation canals in Sindh which were overtopping, internal erosion, structural defects and piping. • Mountassir et al (2014). inferred that overtopping and stability issues in the embankments provides motivation for developing a better understanding of the behavior of the compacted fill under different loading and wetting conditions • Dyer et al. (2007)concluded that failure of embankment was due to seasonal wetting and drying with potential cracking on the crest and side slopes. This can accelerate the rate of weathering and softening of the embankment fill and creates the possibility that water-filled cracks will lower the embankment’s ability to resist the flood.

10. Morris et al. (2007) discussed about the different causes of failure related to embankment earthwork i.e seepage, piping, erosion and slope instability. They concluded that Reason of failure is broadly divided into two modes depending on where the failure generates. First mode is founding strata (settlement, sliding, seepage and piping and uplift pressure) and second mode is embankment structure (slope instability, internal seepage, erosion of outward face and toe). • Modal et al. (2012) investigated the function of geotechnical, geometrical and hydraulic properties on embankment breaching of Moyna drainage basin area using a group analysis based upon vulnerability index for the indicators. A River Embankment Breaching Vulnerability Index (REBVI) was derived based on weightings of bank material to demarcate the risk of vulnerability of the embankment.

11. Methodological approach of River Embankment Breaching Vulnerability Index (Mondal et al, 2012) • This Research is the step forward of the above conducted studies.

12. For study purpose various bunds has been selected on River Chenab in D. G. Khan zone which have the potential for breaching during flood season.

13. The results indicate that Field SPT (N) blows were 14 at RD 147+000 and 18 at RD 157+000. While SPT (N) blows were 17 at RD 25+000 15 at RD 29+000. The description of soil consistency shows the compaction of existing bund strata is firm to stiff. The results of the Permeability test performed in the Field depicts that coefficient of permeability (K) at RD 147+000 and at RD 157+000 is 2.43E-04 and 1.51E-04 respectively. While the coefficient of permeability (K) value at RD 25+000 and RD 29+000 is 1.35E-03 and 1.53E-05 respectively. Field density calculated from undisturbed soil samples recovered during subsurface exploration is 112 pcf and 81 pcf at RD 157+000. The bulk Density was 125 pcf at RD 25+000 and 75 pcf at RD 29+000.

14. Soil classification USCS ASTM D 422 Results SC RD 157 SC RD 147 SC RD25 RD 29 SP-SM ML

15. Unconfined Compressive Strength ASTM D-2166 UCS was performed on undisturbed soil samples taken from Field through SPT UU

16. Permeability Test ASTM D-5084 &2434 Constant Head Permeability test Falling Head permeability test

17. Analysis of the bund structure has been performed considering four different critical scenarios as; • Steady state at Highest Flood Level • Rapid draw down from Highest Flood Level • Steady state at Extreme condition with 3ft free board • Rapid draw down from extreme condition with 3ft free board

18. 25 ' 1 1 3 2 River side 15' Embankment Country side Foundation 15’

20. Hydraulic Conductivity function Volumetric water content function

21. RD147 Discharge at d/s toe =8.19E-005ft3/sec Exit gradient =0.37 safe gradient =0.3 Steady state at Highest Flood Level Rapid draw down from Highest Flood Level Discharge at d/s toe =9.3E-02ft3/sec Exit gradient =0.4 safe gradient =0.3

22. RD147 Discharge at d/s toe =5.61E-05ft3/sec Exit gradient =0.39 safe gradient =0.3 Steady state at Extreme Condition with 3 ft free board Rapid draw down from Extreme Condition with 3 ft free board Discharge at d/s toe = 5.93E-02 ft3/sec Exit gradient =0.44 safe gradient =0.3

24. The analysis of embankment breaching was delineated based on a multi-criteria analysis using bank materials, geotechnical and geometrical parameters. • Ranking of Different Parameters. (1-7):1 means highly ranked and 7 means lowest ranked. (Detailed table on next slide) • Weighting of values within Parameter. (0-6):0 means very less vulnerable and 6 means very highly vulnerable. These values are shown in tabular form (Next Slide)

26. After deriving the normal weights and ranks of all individual parameters were integrated in order to demarcate REBVI in the study area. The equation of REBVI is as follows: REBVI = (RST*WST) + (R BD * W BD) + (R SF * W SF) + (R TH * W TH) + (R BW * W BW) + (R BS * W BS) + ( R WH * W WH). Where R= rank value, W= weight value, ST= Soil Texture, BD= Bulk Density, SF= Safety Factor, TH= Top Height, BW = Base Width of Embankment, BS= Bank Slope, WH= Water Height

28. (Mondal et al, 2012)

29. The SPT value for the selected flood bund indicates that compaction of the existing bund structures is loose. • The exit gradient calculated for the flood bunds by seep/w ranges from 0.003 to 0.44. • The selected flood bunds analyzed using software under different critical conditions shows that flood bund at RD: 147+000 and 157+000 are susceptible to piping failures while flood bunds at RD: 25+000 & RD: 29+000 are marginally safe. • The REBVI value indicates that bund structures at RD: 147+000 and RD: 157+000 have more potential to breaching.

30. It is recommended to carry out health monitoring of all flood bunds on annual basis to reduce losses due to breaching of flood bunds. • Clayey material should be used to make the flood bund impervious. • As most of the flood bunds are susceptible to piping it is recommended to make use of cutoff walls or berms to lengthen the seepage path.

31. The Geotechnical health evaluation of flood bunds should be conducted on other Flood bunds having potential for breaching.

32. Bowles, J. E., “Foundation Analysis and Design”. • Dyer, M, R. Utili , S. and Smith, P. (2007): “The Geotechnical Inspection and Assessment of Flood Defense Embankments” Conference Paper: May 2007 • Fredrick, s. Merritt, Standard Handbook for Civil Engineers • Government of Pakistan Ministry of Water & Power “Annual Flood Report 2015”  • Government of Punjab, Flood inquiry Tribunal “Left Marginal Bund (LMB) Breach of Taunsa Barrage 2010”  • Irrigation Department GOVT. of Punjab (2016); “Geotechnical Investigation for Monitoring the Health of Flood bunds in Punjab” IRR Phy/622 • Mondal, M. Gouri, S. B and Pravar K.S (2012): “Vulnerability Analysis of Embankment Breaching”, International Journal of Geology, Earth and Environmental Sciences ISSN: 2277-2081. • Morris, M. Dyer, M. Smith, P. (2007): “Management of Flood Embankments” A Good Practices Review. Research and Development Technical Report FD2411/TR1. (available at: http//scienceresearch.defra.gov.uk/Document.aspx.)

33. Morris, M. Dyer, M. Smith, P. (2007): “Management of Flood Embankments” A Good Practices Review. Research and Development Technical Report FD2411/TR1. (available at: http//scienceresearch.defra.gov.uk/Document.aspx.) • Manuals of US Army Corps of Engineers for Slope and Seepage Analysis (EM 1110-2-1901 &1902). • Mountassir, G. E., Snche, M., & Romer, E. (2014). An experimental study on the compaction and collapsible behavior of a flood deface embankment fill. Engineering Geology vol. 179, 132-145. • Obuzor, G, N. Kuthia, j, M & Robinson, B, R. (2012). Soil stabilization with lime-activated-GGBS—A mitigation to flooding effects on road structural layers/embankments constructed on floodplains. Engineering Geology, 112-119. • The Seismic design Handbook, Geotechnical design consideration ch.3 • Terzaghi, K (1943), “Theoretical Soil Mechanics”, John Wiley and sons ,Inc, New York.

34. THANK YOU for Your Time & Patience

35. Any Question

36. RD 157 e.g=0.33 Steady state at HFL e.g= 0.34 RD157

37. Steady state at Highest Flood Level Exit gradient =0.21 Critical gradient =0.3 RD 25 Rapid draw down from Highest Flood Level Exit gradient =0.049 Critical gradient =0.3

38. Steady state at Extreme condition with 3 feet free board Steady state at Highest Flood Level Exit gradient =0.26 Critical gradient =0.3 RD25 Rapid draw down from extreme condition with 3 feet free board Exit gradient =0.o72 Critical gradient =0.3

39. Steady state at Highest Flood Level FOS obtained =1.53 FOS Critical =1.5 Exit gradient =0.21 Critical gradient =0.3 RD 29 Rapid draw down from Highest Flood Level FOS obtained =2.12 FOS Critical =1.3 Exit gradient =0.002 Critical gradient =0.3

40. Steady state at Extreme condition with 3 feet free board Steady state at Highest Flood Level FOS obtained =1.48 FOS Critical =1.4 Exit gradient =0.23 Critical gradient =0.3 RD29 Rapid draw down from extreme condition with 3 feet free board FOS obtained =2.08 FOS Critical =1.1 Exit gradient =0.003 Critical gradient =0.3