Total risk rating and stability analysis of embankment dams in the Kachchh Region, Gujarat, India Amit Srivastava ⁎, G.L. Sivakumar Babu Department of Civil Engineering, Indian Institute of Science, Bangalore, 560012, India abstract article info Article history: Received 25 November 2009 Received in revised form 3 June 2010 Accepted 19 June 2010 Available online 28 June 2010 Keywords: Embankment dam Seismic hazard Risk analysis Numerical Earthquake Deformation A method for total risk analysis of embankment dams under earthquake conditions is discussed and applied to the selected embankment dams, i.e., Chang, Tapar, Rudramata, and Kaswati located in the Kachchh region of Gujarat, India, to obtain the seismic hazard rating of the dam site and the risk rating of the structures. Based on the results of the total risk analysis of the dams, coupled non-linear dynamic numerical analyses of the dam sections are performed using acceleration–time history record of the Bhuj (India) earthquake as well as five other major earthquakes recorded worldwide. The objective of doing so is to perform the numerical analysis of the dams for the range of amplitude, frequency content and time duration of input motions. The deformations calculated from the numerical analyses are also compared with other approaches available in literature, viz, Makdisi and Seed (1978) approach, Jansen's approach (1990), Swaisgood's method (1995), Bureau's method (1997), Singh et al. approach (2007), and Saygili and Rathje approach (2008) and the results are utilized to foresee the stability of dams in future earthquake scenario. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Embankment dams are considered to be “structures of public utility” and they always pose some risk to human life and property on their downstream side in the event of an earthquake. The first failure of a dam due to an earthquake, reported in the literature, is Augusta dam, GA, during the 1886 Charleston, SC earthquake (Bureau, 2003). The seismic performance of embankment dams is closely related to the nature and state of compaction of the fill material. Well compacted modern dams can withstand substantial earthquake shaking with no detrimental effects. In contrast, old embankments built from poorly compacted sands and silts or founded on loose alluvium, hydraulic fill dams, and tailing dams represent nearly all the known cases of failure (Bureau, 2003). The dam owners and regulating authorities must ensure that dams are safely operated and present no threat to the public in the case of an earthquake. Owners of dams or officials in-charge of dam safety programs should perform a comparative study and assess the seismic risk associated with different dams and should establish priorities for dam safety risk management and mitigation. On 26th January, 2001, the Kachchh region of Gujarat in India experienced a disastrous earthquake, popularly known as “Bhuj” earthquake, of 7.6 magnitude (M w ). The earthquake caused severe damage to facilities like buildings, embankment dams, ports, roads and bridges and also caused loss of several lives. The state department (Government of Gujarat) estimated that 15.9 million people (50% population of Gujarat) were affected, directly or indirectly, and more than 20,000 cattle were reportedly killed. The estimated economic loss was $5.0 billion. The Kachchh Peninsula, which has a long history of strong earthquakes, is bordered from the north and to the south by ancient rift systems (Bendick et al., 2001). The mainland within these rift systems is subjected to compressional stress and reverse faulting resulting from India's collision with Asia (Chandra, 1977). The first reported historical Kachchh earthquake was the 1819 Allah Bund earthquake. Damaging earthquakes also occurred in 1845, 1856, 1857, 1864, 1903, 1927, 1940, 1956, and 1970 in the Kachchh region with magnitudes ranging from 5.0 to 6.0 (Bapat et al, 1983). The Bhuj earthquake is considered to be the second largest earthquake (M w =7.6) that occurred in the Kachchh paleorift zone in the recorded history after the June 12th 1819 earthquake, which was of magnitude 7.8 (M w ) (Allah Bund EQ). It is also one of the largest continental intra- plate earthquakes that have occurred globally in more than 100 years. 2. Geological features and tectonic settings The tectonic framework of northern India is dominated by two main features: (i) the stable continental craton of peninsular India, and (ii) the collision zone where India and Asia converge along the Himalaya plate boundary zone. Plate tectonic models based on geological and geomorphic data, earthquake slip vectors, and global positioning satellite (GPS)-based plate velocities indicate that the Indian plate is moving north relative to Asia at a rate of 20 ± 3 mm/yr Engineering Geology 115 (2010) 68–79 ⁎ Corresponding author. Tel.:+91 80 22932815; fax: + 91 80 23600404. E-mail addresses: amisri@civil.iisc.ernet.in (A. Srivastava), gls@civil.iisc.ernet.in (G.L.S. Babu). 0013-7952/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.enggeo.2010.06.011 Contents lists available at ScienceDirect Engineering Geology journal homepage: www.elsevier.com/locate/enggeo