Sm Model In The Seismic Response Analysis Of Embankment Dams

It is of practical and theoretical significance to use a reasonable dynamic constitutive model of soil materials and adopt an effective analysis method.In this thesis, scaled memory(SM) model describing the dynamic stress-strain response curves of hysteretic soil materials is introduced comprehensively. SM scales the nonlinear variation of tangential modulus during monotonic loadings into a piecewise linear distribution, which can easily be modified to simulate specific characteristics of soil material behavior during cyclic loadings. SM can simulate dynamic stress-strain response of arbitrary cyclic loadings. SM can be applied to anisotropic materials. SM reconciles empirical and elastoplastic models and our experimental knowledge of soil behavior and is easier and more practical.An incrementally-iterative algorithm with constant stiffness, which combines step-by-step time integration scheme with unbalanced load transfer method, is employed in numerically implementing of the proposed constitutive model. Many iterations are conducted in each time step. Stiffness is constant in each iteration. Nonlinear effect is transformed to equivalent unbalanced node force. The stiffness matrix is kept constant in all incremental loadings and each iteration. Only force vector is changed. So, the efficiency of computing is approved dramatically.A seismic response analysis program of embankment dam is developed, which incrementally-iterative calculating technique is coupled with SM model. The program is competent to conduct the nonlinear time history response analysis and permanent displacement calculation of embankment dam during earthquakes. Taking a monotonic soilfill dam as example, a comparison between the incrementally-iterative numerical technique and the equivalent linearization approach was carried out. It is shown that distribution of dynamic response of dam is mainly alike. The maximum acceleration, the maximum displacement and the maximum shear stress are different obviously. Finally,taking an actual project as example, a nonlinear seismic response analyses is conducted. The numerical results of dynamic analysis obtained by the numerical technique in the paper are capable and practicable.