Analysis On Nonlinear Ground Response In One Dimension Based On The Theory Of Wave Propagation In Two-Phase Media

Wave propagation in saturated, porous media is an important subject in geotechnical and earthquake engineering. Nowadays the method for analyzing nonlinear response of soil layers is equivalent linearization method witch doesn't consider pore-water-pressure. Although it's simple and applicable, with the accumulating of earthquake damage data and further study of response of soil layers, people find that it's unrealistic and even insecure in some cases. The thesis studies further on this subject. A realistic method for analyzing it considering the action of pore-water-pressure is put forward, the objective of which is to put forward an initial method for further studying and analyzing it.Because of the method's complexity, it's very difficult to solve the problem by using analytical method, which is always limited in the very simple cases that are simplified in virtue of various of assumptions. In order to deal with the complicated problems, numerical method is preferable. Therefore, some researches on numerical solution in analyzing the dynamic response of saturated, porous media are done in this paper. The author presents the study results, which include the following content:(1) Simple review many kinds of methods of analyzing response of bottom soil layers and value them by comparison; Recapitulate the development, application and importance of two-phase media theory.(2) Compare various stress-strain nonlinear relationship for soil; analysis its applicable conditions and choose the logical constitutive relationship by using elasto-plastic model (based on the Massing rule and Pyke model).(3) Systematically present two-phase media theory. Dynamical model in saturated soil media can be summed up to three categories: soil dynamics model, Biot's model and Menfulu's model. Based on the supposition of the three categories, the different expression form of these three models are deduced, their similarities and different expression are analyzed too. Meanwhile the suitability of these three models is discussed. One-dimensional wave equation is inferred by using soil mechanics model. Supposing incident waves are normal base shear wave, the diltant soil is the reason why soil and water action and hole-pressure's increase and dissipation is taken into account, closed equations are built on six unknown physical quantities (stress, displacement etc.) under conditions of dry and saturated soils. Discuss its solvability initially, including its decoupling, certainty of type, diagonali- zation, etc.(4) The mechanics model for analyzing earthquake response of soil layers achieves its numerical method by using simple one-dimensional soil layer model. During solution of motion equation, the explicit center difference methods are applied in spatial discretization and finite element in temporal discretization. Boundary applies Multi-transmitting boundary considering various of conditions (the interface between base rock and covering soil layers, boundary of saturated and dry soil layers, free surface boundary, etc.). At the late period of the thesis consider dilatancy and plastic softening.(5) comply Fortran 95 calculated program and ralidate it based on Nonlinear response in one dimension on the theory of two-phase media. Then proceed with calculation examples and compare its result with those of normal equivalent linearization method. Analyze water's effect on earthquake response.At last, the author concludes the study of the thesis, points out its problems and discusses the future research.