th 13th -14 March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE

Lessons Learned from after the Major Earthquake on Nov. 12, 2017

Kawa Z. Abdulrahman, Omed S. Q. Yousif, Younis Alshkane, Abdulrahman Khani, Tareq Battal, Salar Kareem Hama University of Sulaimani DARBANDIKHAN DAM

• Darbandikhan dam is a multi-purpose rock-fill dam located on the approximately 65 km south-east of city and 230 km north-east of Baghdad city (Iraq). • The dam has a height of 128 m, length of 445 m, and 17 m crest width at elevation 495 m. The construction of the dam has been completed in 1961. • The total capacity of the Darbandikhan reservoir is 3 km3 at the normal pool level (El. 485.00 m).

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE DARBANDIKHAN DAM

Figure 1. Darbandikhan Dam location/ Iraq (google map).

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE DARBANDIKHAN DAM

Figure 2. Maximum Cross Section of Darbandikhan Dam.

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE DARBANDIKHAN DAM

Figure 3 Profile of the Darbandikhan Dam - Looking Upstream

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE EARTHQUAKE PROPERTIES • A strong earthquake with a moment magnitude of 7.3 (Mw = 7.3) occurred on November 12, 2017, near the Iran-Iraq border (220 km northeast of Baghdad, Iraq) (USGS, 2021). • The event commonly referred to as the Ezgeleh Earthquake and resulted in 500 victims and about 12000 homeless. • It was the most disastrous earthquake that has affected the Iraq/Iran border since 1909 (USGS, 2021). The earthquake had lasted for about 30 secends (long duration).

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE DARBANDIKHAN DAM

Figure 4: Earthquake intensity and extent (adapted from USGS, 2017)

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE 4. DATA COLLECTION

• In the days following the Azgala earthquake, a team of engineers and geologists carefully surveyed the Darbandikhan dam. • The data collected in two stages (i.e. Visual inspection & Detailed Inspection). • The aim of the survey was to determine the locations of cracks, displacements, and abnormal appearances that caused by the earthquake. • The horizontal and vertical offset of cracks were measured. The movements and settlements were determined relative to control points located on bedrock.

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE VISUAL INSPECTION

Figure 5. Visual inspection just after the earthquake.

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE VISUAL INSPECTION

• The cracks occurred due to the earthquake were mostly along the crest of the dam that ran mainly in the longitudinal direction, and some transverse cracks at the abutments. • However, there were no differences in elevation between the two sides of the transverse cracks on the crest of the dam except that the one next to the spillway wall.

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE VISUAL INSPECTION

Figure 6. Cracks pattern

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE VISUAL INSPECTION

Figure 7. Cracks pattern

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE VISUAL INSPECTION

Figure 8: The crack at the contact between the spillway and the embankment

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE VISUAL INSPECTION Many fallen rocks were observed on the crest of the dam, especially near the abutments. The cracks and fallen rocks were then documented.

Figure 9: Rockfill.

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE VISUAL INSPECTION

Figure 10: Rockfill next to the spillway.

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE VISUAL INSPECTION

Figure 11: Left bank sliding

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE DETAILED SAFETY INSPECTIONS

The detailed safety inspections included the following actions: 1. Geodetic survey (48 cm, ∆H/H=0.38%). 2. Geophysical investigation (GPR & MASW) 3. Test pits (Trenching) 4. Continues Drilling in the clay core 5. Seepage rates and piezometer readings 6. Under water inspection (CREA Co. Czech Republic)

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE TEST PITS (TRENCHING) Several test pits were dug at the crack’s locations, all the cracks on the crest were superficial cracks (i.e. not extending to the core) except the transverse crack next to the spillway. Transverse Crack

Figure 12: Test pit.

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE TEST PITS (TRENCHING)

Figure 13: The crack at the contact between the spillway and the embankment

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE CONTINUOUS DRILLING IN THE CLAY CORE

• In order to check the condition of the clay core at the area close to the spillway. Three boreholes at three locations close to the spillway were drilled using a continues method of drilling. • Visual inspection was then carried out on the extracted cores. • In addition, to check the strength of the clay core, an in-situ test was carried out on the clay core samples using a pocket penetrometer instrument.

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE CONTINUOUS DRILLING IN THE CLAY CORE

Furthermore, constant-head tests were carried out for determining the insitu hydraulic conductivity of clay core in which the same boreholes. According to the results, concentrated seepage did not happen. In addition, the hydraulic conductivity of the borehole was very small; between 0.05 and 0.248 m/year. The obtained value of the hydraulic conductivity was close to the original value of the hydraulic conductivity of the material in the dam core; 0.032 m/year

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE CONTINUOUS DRILLING IN THE CLAY CORE

Figure 14. Clay core log using continuous core method

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE SEEPAGE RATES

Figure 15. Right abutment gallery seepage versus pool elevation.

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE Under Water Inspection

Figure 16: Under Water Inspection . 13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE HOW THE SAFETY OF THE DAM WAS ASSURED?

• Once the safety of the spillway and the bottom outlets has been checked, it was decided to lower the water level in the reservoir in order to investigate the lower parts of the dam and to reduce the water pressure applied to the dam. • The water level in the reservoir was then gradually lowered from the elevation 471.9 m to the elevation 464 m (i.e. 7.9 m) in about two months. • Due to the awareness and cautions about whether there were cracks in the lower parts of the dam or not, the water level was not allowed to rise above elevation 470 m during 2018.

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE HOW THE SAFETY OF THE DAM WAS ASSURED?

• However, in 2019, based on the results obtained from the drilled boreholes and on the promised information regarding the behavior of Earth Core Rockfill (ECRD) subjected to major earthquakes, it was decided to gradually raise the water level in the reservoir. • The decision of rising water level in the reservoir in 2019 was based on the academic findings and observations mentioned in (Pells & Fell, 2002; Fell et al., 2008; Zomorodian & Moghadam, 2011).

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE HOW THE SAFETY OF THE DAM WAS ASSURED?

• According to a statistical analysis carried out by (Pells & Fell, 2002) the depth of cracks that occurred in embankment dams due to earthquakes ranges from 15 to 100 times the width of the crack at the crest. • For Darbandikhan dam, the width of the major transverse crack that occurred in the clay core next to the spillways structure was about 16 cm. So, the estimated depth of this major crack should be between 2.4 m and 16 m from the top of the clay core (i.e. it may go down from elevation 490.6 m to elevation 479m).

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE HOW THE SAFETY OF THE DAM WAS ASSURED?

• Fell et al., (2008) as cited in (USBR, 2015) stated that erosion in clay cores in embankment dams may not occur until the following two conditions fulfilled; • 1- The width of the transverse cracks reaches 1 or 2 inches and’ • 2- The hydraulic gradient approaches 0.5 or more. • Furthermore, the width of possible cracks in clay cores may be reduced or closed due to swelling by the wetting process. • However, the upstream and the downstream wide cohesionless filters of Darbandikhan dam will contribute to the crack filling or self-healing process should any crack exist in the core.

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE HOW THE SAFETY OF THE DAM WAS ASSURED?

• From all of the above analyses and the results of the various investigations, the authorities of Darbandikhan dam concluded that there were no problems severe enough to threaten the safety of the dam and that the dam was safe and could store water to its full capacity. • Accordingly, in May 2019, the water level in the Darbandikhan reservoir was raised to the elevation 484.28 m which is only 0.72 m below the maximum operational level.

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE CONCLUSIONS

• From the results of the inspections and the evaluations, the following conclusions can be drawn: • Adequate design and construction of dams can help them pass through even large earthquakes. • The adopted measures used for evaluation and remediation of the earthquake- induced damages in Darbandikhan dam were dependable for checking dam safety.

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE ACKNOWLEDGMENT

• The authors are very grateful to the personnel in Derbandikhan Dam Directorate and General Directorate of Dams and Reservoir (Iraq) especially Mr. Shaker Hmwd Nda (Senior Engineer), Mr. Hemn Ahmed Abdulla (Engineer), Mr. Azad Maarwf Mohammed (Senior Engineer), Mr. Kadhm Sahar Jabr (Senior Engineer), Mr. Abo Bakr Ahmed Husen (Senior Geoligist). Special thanks to Dr. Bakhtyar Qader Aziz (Professor in Geology Science) for providing valuable information on geophysical methods.

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE REFERENCES

• Bowles, J. E. (1988). FOUNDATION ANALYSIS AND DESIGN. FOURTH EDITION. https://trid.trb.org/view/311245 • Chen, H. (2009). Lessons learned from Wenchuan earthquake for seismic safety of large dams. Earthquake Engineering and Engineering Vibration, 8(2), 241–249. https://doi.org/10.1007/s11803-009-9066-8 • Correia Dos Santos, R. n., Caldeira, L. m. m. s., & Maranha Das Neves, E. (2015). Experimental study on crack filling by upstream fills in dams. Géotechnique, 65(3), 218–230. https://doi.org/10.1680/geot.14.P.198 • Davoodi, M., Sakhi, M. A., & Jafari, M. K. (2008). Comparing Recorded Earthquake Signals of MS Embankment Dam with Numerical Modeling Results. 14th World Conference on Earthquake Engineering, Beijing, China, October, 12–17. • Fell, R., Foster, M. A., Cyganiewicz, J., Sills, G., Vroman, N., & Davidson, R. (2008). Risk analysis for dam safety: A unified method for estimating probabilities of failure of embankment dams by internal erosion and piping. Bureau of Reclamation, US Army Corps of Engineers, UNSW, URS Australia. North Sydney, 4–4. • Houqun, C. (2008). Consideration of dam safety after Wenchuan earthquake in China. Paper of ―China Day‖, 14th World Conference on Earthquake Engineering, Beijing, China, October, 12–17. • Pells, S., & Fell, R. (2002). Damage and cracking of embankment dams by earthquakes and the implications for internal erosion and piping. University of New South Wales, School of Civil and Environmental Engineering. • Reclamation (USBR), U. B. of. (1990). Earth manual, part 2. Third Ed., Materials Engineering Branch, Research Laboratory Services Div., Denver. • Sêco e Pinto, P. (2010, May 24). Understanding Seismic Embankment Dam Behavior Through Case Histories. International Conferences on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics. https://scholarsmine.mst.edu/icrageesd/05icrageesd/session10/10 • Seed, H. (1981, April 26). Earthquake-Resistant Design of Earth Dams. International Conferences on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics. https://scholarsmine.mst.edu/icrageesd/01icrageesd/session07/23 • USBR. (2015). IV-4. Internal Erosion Risks for Embankments and Foundations. U.S. Dept. of the Interior, Bureau of Reclamation. https://fdocuments.in/document/iv-4-internal-erosion-risks- for-embankments-and-erosion-risks-for-embankments.html • USGS. (2021). M 7.3—29km S of Halabjah, Iraq. https://earthquake.usgs.gov/earthquakes/eventpage/us2000bmcg/executive • Yamaguchi, Y., Kondo, M., & Kobori, T. (2012). Safety inspections and seismic behavior of embankment dams during the 2011 off the Pacific Coast of Tohoku earthquake. Soils and Foundations, 52(5), 945–955. https://doi.org/10.1016/j.sandf.2012.11.013

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE REFERENCES

13th -14th March 2021 1ST BAGHDAD INTERNATIONAL WATER CONFERENCE