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Numerical Analysis of Earthquake Response of an Ultra-High Earth-Rockfill

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Numerical Analysis of Earthquake Response of an Ultra-High Earth-Rockfill EGU Journal Logos (RGB) Open Access Open Access Open Access Advances in Annales Nonlinear Processes Geosciences Geophysicae in Geophysics Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Open Access Open Access Nat. Hazards Earth Syst. Sci. Discuss.,Natural 1, 2319–2351, Hazards 2013 Natural Hazards www.nat-hazards-earth-syst-sci-discuss.net/1/2319/2013/ and Earth System doi:10.5194/nhessd-1-2319-2013and Earth System NHESSD Sciences Sciences © Author(s) 2013. CC Attribution 3.0 License. 1, 2319–2351, 2013 Discussions Open Access Open Access Atmospheric Atmospheric This discussion paper is/has been under review for the journal Natural Hazards and Earth Chemistry Chemistry Numerical analysis System Sciences (NHESS). Please refer to the corresponding final paper in NHESS if available. and Physics and Physics of earthquake Discussions response Open Access Open Access Atmospheric Atmospheric W. X. Dong et al. Measurement Measurement Techniques Techniques Numerical analysis of earthquake Discussions Open Access Open Access Title Page response of an ultra-high Biogeosciences Biogeosciences Abstract Introduction earth-rockfill dam Discussions Conclusions References Open Access Open Access W. X. Dong, W. J. Xu, Y. Z. Yu, andClimate H. Lv Climate Tables Figures of the Past of the Past Department of Hydraulic Engineering, Tsinghua University, Beijing, China Discussions J I Open Access Received: 18 April 2013 – Accepted: 10 May 2013 – Published: 28 May 2013 Open Access Earth System J I Correspondence to: Y. Z. Yu ([email protected])Earth System Dynamics Dynamics Back Close Published by Copernicus Publications on behalf of the European GeosciencesDiscussions Union. Full Screen / Esc Open Access Geoscientific Geoscientific Open Access Instrumentation Instrumentation Methods and Methods and Printer-friendly Version Data Systems Data Systems Interactive Discussion Discussions Open Access Open Access Geoscientific Geoscientific Model Development Model Development2319 Discussions Open Access Open Access Hydrology and Hydrology and Earth System Earth System Sciences Sciences Discussions Open Access Open Access Ocean Science Ocean Science Discussions Open Access Open Access Solid Earth Solid Earth Discussions Open Access Open Access The Cryosphere The Cryosphere Discussions Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Abstract NHESSD Failure of high earth dams under earthquake may cause disastrous economic damage and loss of lives. It is necessary to conduct seismic safety assessment, and numer- 1, 2319–2351, 2013 ical analysis is an effective way. Solid-fluid interaction has a significant influence on 5 the dynamic responses of geotechnical materials, which should be considered in the Numerical analysis seismic analysis of earth dams. The initial stress field needed for dynamic computation of earthquake is often obtained from postulation, without considering the effects of early construction response and reservoir impounding. In this study, coupled static analyses are conducted to simu- late the construction and impounding of an ultra-high earth rockfill dam in China. Then W. X. Dong et al. 10 based on the initial static stress field, dynamic response of the dam is studied with fully coupled nonlinear method. Results show that excess pore water pressure accumulates gradually with earthquake and the maximum value occurs at the bottom of core. Accel- Title Page eration amplification reaches the maximum at the crest as a result of whiplash effect. Abstract Introduction Horizontal and vertical permanent displacements both reach the maximum values at 15 the dam crest. Conclusions References Tables Figures 1 Introduction J I With the development of construction technology and a better understanding of the earth-rockfill dams’ mechanism (Yasuda and Matsumoto, 1993; Hunter and Fell, 2003; J I Soroush and Jannatiaghdam, 2012), high earth-rockfill dams have become a more Back Close 20 competitive type of dams. A number of high core earth dams and concrete faced rockfill dams (CFRDs) with heights of more than 200 ∼ 300 m are being under construction Full Screen / Esc or to be built in Southwest China located in the Himalayas seismic belt with heavy potentially seismic activity. Printer-friendly Version Failures of earth dams, especially for high earth dams with a height more than 200 m, Interactive Discussion 25 may cause catastrophic economic damage and loss of lives. Among these failures, earthquake attack is one of the major causes. In general, the principal failures induced 2320 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | by earthquake attack can be classified as sliding failure, liquefaction failure, longitudi- nal cracks, transverse cracks, and piping failure (Chen, 1995). Numerical computation NHESSD based on constitutive model of geotechnical materials is one of the effective ways to 1, 2319–2351, 2013 conduct seismic analyses and seismic safety assessment. 5 Earth dams are complicated nonhomogeneous geotechnical structures composed of different materials such as rockfill and clayey soils. This results in great difficulty to Numerical analysis analyse and predict the responses of earth dams under various conditions, such as of earthquake construction, reservoir impounding and earthquake attacks (Costa and Alonso, 2009; response Seo and Ha, 2009). Therefore, existing theories and numerical analyses of earth-rockfill W. X. Dong et al. 10 dams include many simplifying assumptions (Prevost et al., 1985). Pseudo static method (Seed and Martin, 1966) is largely used in the numerical anal- yses to assess the seismic response of earth dams. In this approach, seismic effect Title Page on dam body is considered with an equivalent static force, which is the product of soil mass multiplied by a seismic coefficient, and soil is assumed as rigid-perfectly plastic Abstract Introduction 15 behaving. Newmark (Newmark, 1965) presented the important concept that the seismic sta- Conclusions References bility of slopes is more important rather than the traditional factor of safety, and he Tables Figures proposed a double integration method to compute the permanent displacement under cyclic loading, which is based on the concept of analyses of a rigid block sliding on J I 20 a plane. Once the acceleration exceeds the “yield acceleration”, permanent displace- ment can be obtained by double integrating the acceleration. J I Up to now, most numerical earthquake response analyses of earth-rockfill dams Back Close were conducted using equivalent linear models, in which shear modulus and damping ratio are obtained by iterative procedure (Abdel-Ghaffar and Scott, 1979; Mejia et al., Full Screen / Esc 25 1982). Cascone and Rampello (2003) evaluated the seismic stability of an earth dam via the decoupled displacement analysis to compute the earthquake-induced displace- Printer-friendly Version ments. Parish et al. (2009) performed a study of the seismic response of a simplified typical Interactive Discussion earth dam using the FLAC3D software. Non-associated Mohr–Coulomb criterion was 2321 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | adopted to describe the behaviour of both shells and core of the earth dam. Their analyses showed that plasticity should be considered in the analysis of the seismic NHESSD response of the dam, as it leads to a decrease in the natural frequency of the dam, 1, 2319–2351, 2013 which could significantly affect the seismic response of the dam. However, this study 5 did not consider the fluid-skeleton interaction, which should have a significant influence on the seismic response of earth dams. Numerical analysis Siyahi and Arslan (2008) studied the dynamic behaviour and earthquake resistance of earthquake of Alibey earth dam located in Turkey by adopting the OpenSees software (Open Sys- response tem for Earthquake Engineering Simulation) (2000). Elastoplastic constitutive models W. X. Dong et al. 10 of soils such as pressure dependent and independent multi-yield materials were imple- mented in the analyses. They obtained the permanent displacements and concluded that the liquefaction effect is not significant. Title Page However, so far, application of solid-fluid coupled elasto-plastic dynamic analyses in safety assessment of earth-rockfill dams is not much. Furthermore, the initial stress Abstract Introduction 15 field needed for dynamic computation is often provided without considering the effects of early construction and reservoir impounding. Conclusions References In this work, the static and dynamic responses of Nuozhadu high earth-rockfill dam Tables Figures have been studied by solid-fluid coupled nonlinear method, since solid-fluid interaction has a significant influence on the behaviour of earth dams. First, the dam site and J I 20 detailed design data are introduced. The adopted numerical analysis method and soil constitutive model parameters are presented. J I In the static analysis, the practical construction was simulated. Then, reservoir im- Back Close pounding was simulated by conducting solid-fluid coupled analysis. At last, the coupled nonlinear dynamic analyses were conducted based on the initial Full Screen / Esc 25 stress field obtained from the preceding computation. The acceleration component of the El Centro 1940 earthquake was chosen as seismic motion. The excess pore water Printer-friendly Version pressure, acceleration responding, and permanent displacements induced by seismic move are presented and analysed. Interactive Discussion 2322
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