Nonlinear seismic response analysis of earth dams

The objective of this paper is to propose a general and efficient numerical procedure for analysing the dynamic response of geotechnical structures, which are considered as both nonlinear and two phase systems. In Section 2, the appropriate coupled dynamic field equations for the response of a two-phase soil system are briefly reviewed. The finite element spatial discretization of the field equations is described and time integration for the resulting nonlinear semi-discrete finite element equations is discussed. In Section 3, iterative techniques are examined for the solution of the global nonlinear system of finite element equations. A large amount of computational effort is expended in the iterative phase of the solution and so the iterative procedure used must be both reliable and efficient. The performance of three iterative procedure is examined: Newton Raphson, Modified Newton Raphson and Quasi-Newton methods, including BGFS and Broyden updates. Finally, in Section 4, the elasto-plastic earthquake response analysis of a two phase nonhomogeneous earth dam is presented. Extensive documentation exists1 for the particular problem selected including recorded earthquake motions at the base and crest of the dam. The results of the numerical calculations are compared to the recorded response of the dam.