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The objective of this paper is to estimate permanent displacements of Tehri dam due to an earthquake of magnitude M
w
= 8·5, the occurrence of which has a high probability in the region, and for an earthquake of magnitude M
w
= 7·0, for which the dam has been currently designed. A two-dimensional finite element analysis and five different semi-empi...
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Context 1
... detail description of the dam is given by Thatte (Thatte 1992). Figure 1 shows a typical cross-section of the dam assumed in the present analyses. The locations of the slide surfaces are shown in figure 2. Almost no published information is available on the in situ strengths of the dam materials. ...
Context 2
... (1997) presented a relationship, figure 10, which relates relative crest settlement (%) to the Earthquake Severity Index (ESI). Bureau has defined the earthquake severity index (ESI) by the following empirical equation: ...
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... ground motion was scaled to 0·23 g and 0·45 g, and applied at the base of the dam to compute the permanent deformations of the dam during the earthquakes. Figure 11 shows the selected ground motion scaled to 0·23 g. The numerical analyses predicted no liquefaction of the dam and its foundation during the earthquakes. ...
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... numerical analyses predicted no liquefaction of the dam and its foundation during the earthquakes. Figures 12 and 13 show the deformed dam geometry at the end of 23 sec of 0·23 g and 0·45 g earthquake motions, respectively. In both the figures deformations are magnified 100 times. ...
Context 5
... vertical deformation was computed at the crest of the dam while horizontal deformation was obtained at the upstream berm of the dam for both the earthquakes. Figure 14 shows the vertical displacements at the crest of the dam for the 0·23 g and 0·45 g earthquakes. Figure 15 shows the horizontal displacements of the upstream berm of the dam for both the earthquakes. ...
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... 14 shows the vertical displacements at the crest of the dam for the 0·23 g and 0·45 g earthquakes. Figure 15 shows the horizontal displacements of the upstream berm of the dam for both the earthquakes. Since unusually large freeboard is maintained for this dam, in neither earthquake cases there will be overtopping of the dam. ...
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Citations
... A precise repeat of the 1803 earthquake would shake the dam with EMS intensity ≥7 (0.3g) for approximately 5 s, with a 'fling' exceeding 4 m (Bilham 2016) approximately normal to the face of the dam. Calculations reveal that this might lead to crest settlement threatening the integrity of the dam (Sengupta 2010). ...
This article summarizes recent advances in our knowledge of the past 1000 years of earthquakes in the Himalaya using geodetic, historical and seismological data, and identifies segments of the Himalaya that remain unruptured. The width of the Main Himalayan Thrust is quantified along the arc, together with estimates for the bounding coordinates of historical rupture zones, convergence rates, rupture propagation directions as constrained by felt intensities. The 2018 slip potential for fifteen segments of the Himalaya are evaluated and potential magnitudes assessed for future earthquakes should these segments fail in isolation or as contiguous ruptures. Ten of these fifteen segments are sufficiently mature currently to host a great earthquake (M w ≥ 8). Fatal Himalayan earthquakes have in the past occurred mostly in the daylight hours. The death toll from a future nocturnal earthquake in the Himalaya could possibly exceed 100 000 due to increased populations and the vulnerability of present-day construction methods.
... Some numerical studies also suggest that the simplified methods do not always give a conservative estimate of deformation (e.g. Ghanooni and MahinRoosta, 2002, Feizi-Khankandi et al., 2009, Nejad et al., 2010, Sengupta, 2010. Strenk and Wartman (2011) performed a series of probabilistic analyses to evaluate the permanent deformations predicted by the rigid block and decoupled methods. ...
... where can be taken equal to of Seed and Idriss (1970), based on the following relationship for the shear modulus of granular material: ...
... where is the average mean effective stress at the base of the dam. 2 ranges from 80 to 180 for gravels (Kramer, 1996) and 52 to 70 for sands (Seed and Idriss, 1970). ( 2 ) represents the mean value of 2 for different materials used in the dam. ...
The simplified Newmark-Type methods are recommended in many technical guidelines for evaluation of the seismic induced deformations and as a screening tool for performance-based seismic design of embankments. These methods are mostly known as a systematic approach to identify embankments with marginal factor of safety, assuming that they are always able to provide conservative estimates of displacements. Recent studies, however, have demonstrated that application of the simplified Newmark-type methods may not be conservative in some cases, especially when the tuning ratio of a dam is within a certain range. In this paper, the reliability of the simplified methods is examined based on the existing thresholds proposed in the literature for tuning ratio, considering the geometry and type of embankment and the seismic activity characterization. A practical framework for assessing the reliability of simplified Newmark-type methods is described and its effectiveness is evaluated in the study of seismic behavior of Zipingpu Dam where none of the simplified methods was able to predict the order of deformation experienced by the dam under a recent earthquake event. 1 INTRODUCTION In the design of a new dam, or in evaluating the seismic performance of an existing dam, it is imperative to evaluate the potential deformations of the dam due to earthquake loading. The magnitude of the crest settlement of a dam must be less than the free board of the dam to prevent overtopping and breach. The guidelines on performance-based design of embankments have proposed different approaches for evaluation of earth dams under earthquake loading, ranging from simplified Newmark-Type procedures to complex stress-deformation analyses. Among these approaches, the simplified Newmark-Type methods are more popular in practice due to their simplicity and inexpensive application. However, recent studies show that these methods do not always give a conservative estimate of deformation of dams under earthquake loading (e.g. Rathje and Bray 2000, Wartman et al. 2003, Nejad et al. 2010, Meehan and Vahedifard 2013). There are few proposed thresholds in the literature for the range of applicability of the Newmark-Type methods; e.g., Kan et al. (2017) proposed a framework to convert these thresholds to measurable practical engineering parameters related to the height and type of the embankment, and the seismic activity of the site. This framework and its application is further reviewed in the present paper from performance-based design perspective. The effectiveness of the proposed framework is also evaluated using a recent case history of earthquake effects on Zipingpu Dam, a well-compacted modern rockfill dam which suffered large deformations during 2008 Wenchuan Earthquake in China. 2 NEWMARK-TYPE SIMPLIFIED METHODS Newmark (1965) proposed a method for evaluation of deformation of embankments due to earthquake loading, which became the basis for further theoretical research in this field. Newmark assumed that the behavior of a potential sliding mass in an embankment is similar to the behavior of a sliding block on an inclined surface. The block slides only if the earthquake acceleration becomes larger than the yield acceleration of the block. The yield acceleration of a potential sliding block (í µí± í µí±¦) is a horizontal acceleration which results in yielding (or failure) along a slip surface with irrecoverable deformation and can be evaluated from a limit equilibrium analysis. The displacement of a block under earthquake loading can be calculated by double integration of the earthquake acceleration exceeding the yield acceleration of the block. The original Newmark method is often referred to as the "rigid sliding block" method. Makdisi and Seed (1978) modified and improved the original Newmark method by considering the effect of deformability of embankment dams during earthquake loading. This contribution was based on two-dimensional finite element analyses of some real and hypothetical dams with heights ranging from 30 m to 60 m, constructed of compacted cohesive or stiff cohesionless materials. The analyses were based on the assumptions that the stiffness of the material is non-linear and is dependent on
... The ground motion was chosen such that its frequency content matches with the predominant time period of the dam, which typically lies between 0.1 sec and 1 sec (ref. 14). The selected earthquake motion has a predominant time period, PGA, velocity and displacement of 0.34 sec, 153.036 cm/s 2 , 8.402 cm/s and 56 cm respectively. ...
... where T is the fundamental period of the dam (= 0.218 sec in the present case). Based on the procedure by Sengupta 14 , the relative displacements of the dam at 1/3rd height are found to be 2 mm for the upstream side and 76 mm for the downstream side. No significant deformations are observed at 2/3rd and full height of the dam from the above methodology. ...
This article presents the permanent deformation of an earthen dam located in the vicinity of a safety related structure for Mw = 6.5 design basis earthquake. A nonlinear 2D dynamic analysis using a real earthquake motion compatible with the design spectrum was performed to check the earthquake-induced deformations of the dam. Deformations of the dam were also estimated by semi-empirical and empirical methods such as Seed and Makdisi's method, Newmark's double integration method, Jansen's method and Swaisgood's method. Results from different methods are compared to obtain a range for the value of permanent deformations of the dam. It is observed that the lateral deformation obtained by Seed and Makdisi's method is the highest while Jansen's method predicts the highest crest settlement. The crest settlement of the dam is found to vary between 11.8 mm and 17.8 mm, which is within the safety limits according to IITK-GSDMA guidelines.
... In evaluation of the performance of Tehri Dam with a height of 260 m under an earthquake with a magnitude of 7, Sengupta (2010) reported that the displacement of the dam crest using the Makdisi and Seed method was around half of the deformation obtained from a stress-deformation analysis. Although in another analysis with a stronger earthquake (magnitude 8.5), the Makdisi and Seed method showed an extremely large crest displacement of 7.5 m while the stress-deformation analysis predicted a settlement of 1.1 m. ...
The simplified procedures for evaluation of the earthquake-induced displacement in earth and rockfill dams are widely used in practice. These methods are simple, inexpensive, and substantially less time consuming as compared to the complicated stress–deformation approaches. They are especially recommended to be used as a screening tool, to identify embankments with marginal factor of safety, assuming that these methods always give conservative estimates of settlements. However, recent studies show that application of these methods may not be conservative in some cases, especially when the tuning ratio of a dam is within a certain range. In this paper, the fundamental theory behind the simplified methods is critically reviewed. A case in which the results of the simplified methods are reportedly nonconservative is investigated in detail and possible reasons are discussed. The reliability of the simplified methods is examined here based on the existing thresholds proposed in the literature and accounting for the embankment geometry and type, and for the seismic activity characterization, and a practical framework is proposed accordingly. The effectiveness of this framework is evaluated in the study of seismic behaviour of a rockfill dam where all simplified procedures failed to predict the order of deformation experienced by the dam under a recent earthquake event.
... The displacement of the dam crest predicted by numerical analysis using FLAC software was predicted to be 1.2 m while the simplified method estimated the deformation to be around 0.55 m. In evaluation of the earthquake resistance of Tehri Dam with a height of 260 m and under a magnitude 7.0 earthquake, Sengupta (2010) reported that the displacement of the dam crest evaluated by the simplified method to be around half of the deformation obtained from a numerical analysis using PLAXIS software, although in another analysis with a stronger earthquake (magnitude 8.5) the simplified method resulted in 7.5 m crest displacement while the numerical model predicted a settlement of around 1.1 m. ...
The current research focuses on the dynamic study of the 260.5 m high Tehri dam, which spans the Bhagirathi River in India’s Garhwal Himalayas. Since it was constructed in seismic zone-IV, there is a significant risk of an earthquake with a magnitude of 7–8.5 or more on the Richter scale in the area. Earthquakes with hypo-central distances of 50.6 km and 89.7 km from Tehri region occurred in the years 1991 (Uttarkashi earthquake) and 1999 (Chamoli earthquake), respectively, according to the data stored in Strong-Motion Virtual Data center (VDC). Hence, the repetition of such seismic activities in the Tehri region is highly probable. In this paper, numerical modeling is carried out using finite element analysis-based ABAQUS software to simulate a magnitude 7.8 earthquake in Nepal and calculated spectral accelerations. Response spectrum graphs are prepared using SEISMOMATCH, which are validated with IS: 1893:2016 (PART-1), and the spectral accelerations are scaled to 7.8 magnitude Nepal Earthquake in the Himalayan belt, with the help of which maximum acceleration is calculated. Finite element method and approximate methods are compared to obtain the crest acceleration in dam and give satisfactory results.KeywordsSeismic gapNatural frequencyShear wave velocityDynamic analysis
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Dams are very important in Ghanas economic development and environmental improvement. Although Ghana dams are seismically far from the active zone, accurately analysed dams should be evaluated since failure could severely impact the people in the flood environment and the regions economy on a large scale. This paper proposes a numerical procedure for the static, slope stability, and dynamic analysis of the Akosombo embankment dam. Nineteen horizontal acceleration time histories recorded data was used based on Maximum Design Earthquake (MDE), Maximum Credible Earthquake (MCE), Design Basis Earthquake (DBE) and Operating Basis Earthquake (OBE) data. The numerical results estimated showed that the Akosombo embankment dam is likely to experience moderate deformations during the different design earthquakes. The result also indicated that non-linear analysis capable of capturing dominant non-linear mechanisms could be used to assess the stability of embankment dams. The factor of safety (FS) calculated was greater than 1.5 for high reservoir, rapid drawdown condition and low reservoir condition whereas, the FS values were found to be 1.42 for slow drawdown condition.
Water and energy supplies are the key factors affecting the economic development and
environmental improvement of Turkey. Given their important role and the fact that a large part of Turkey is
in seismically active zones dams should be accurately analyzed since failure could have a serious impact on
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Bingöl (2003) earthquake data was used based on Maximum Design Earthquake (MDE) data. Numerical
analysis showed that, the Pamukcay dam is likely to experience moderate deformations during the design
earthquake but will remain stable after the earthquake is applied. The result also indicated that, non-linear
analysis capable of capturing dominant non-linear mechanism can be used to assess the stability of
embankment dams.
