Rockfill Dam Seismic Dynamic Response Of The Nonlinear Numerical Analysis

A number of high concrete-faced rockfill dams (CFRDs) with the height ofmore than 200m are being under construction or to be built in the Southwest areaof China with potentially heavy seismic activity. Therefore, the safety of thesehigh CFRDs subjected to strong earthquake shaking in addition to reservoiringbecomes a crucial issue in goveming their whole perfOrmance. In this thesis.dynamic seismic response and earthquake-resistant behavior of highconcrete-faced rockfill dams are studied based on numerical finite elementanalvses.In order to incorporate the nonlinear characteristics of rockfill materials. theequivalent linearization procedure is incorporated into both two-dimensional andthree-dimensional finite element analyses. Modified versions of the computercodes QUAD4 and THREE8 developed by Seed et al are updated in order toeffectively capture the structural or geometrical characteristics of concrete-facedrockfill dam. A special interface element, e.g., Goodman's joint element. isemployed to reproduce behavior of interface between reinforced concrete slaband rockfills. A modified formulae of dynamic water pressure given byHwtong Xu on the basis of Westergaard's theory is used to takeseismically-induced water pressure on the inclined upstream dam face intoconsideration.The revised analysis method together with the computer program is aPpliedto evaluate dynamic response of CFRDs under the given earthquake-inducedground motion. Hong Jiadu concrete-faced rockfill dam is used as the numericalexample. A vast number of numerical computations are conducted and pararnetricstudies are made. Both two-dimensional and three-dimensional computations aremade and then the numerical results are compared. The effects of some factors-such as dynamic parameters of rockfills including maximum dynamic shearmodulus. empirical curi'es of shear modulus and damping ratio \'eq.ing withshear strain level. reservoiring. input ground motions. on dynamic response ofCFRD are investigated. The performances of different t}'pes of interface elementsare compared. Three-dimensional effects due to irregular shape of can}'on areshoun compared t'.ith 2-D anal}'ses. Numerical results of d}'namic anal}1sesincluding the accelerations and dynamic shear stresses of rockfill embankInent aswell as the dynamic stresses of concrete slab are presented for differentconditions.Meaningful conclusions are given based on numerical results. These will behelpful to earthquake-resistant design of concrete-faced rocanll dams. From thestandpoint of engineering practice, present nurnerical solutions can give a betterunderStanding of both the acceleration ofrockfill body and the dtwc sbess ofconcrete slab compared with the conventional methods.