Non-linear Damage Mechanics Theory Of Coupled Fluid-Solid With Numerical Analysis Of Geo-Materials

Geo-materials are the production of nature, and are also multiphase systems which include different kinds of randomly distributed defections, such as micro-cracks, voids and so on. The seepage of fractured geo-materials takes an action on the distribution of stress fields. Simultaneously, the changes of stress fields make the defections become deform, and affect the seepage characteristics of them, too. Therefore, the seepage of fractured geo-materials is not only a complex and hot problem to be studied recently, but also has an important value in theory and the application of engineering fields, which is mainly the coupled problem between the multiphase fields (stress fields, distortion fields, damage fields, seepage fields, and so on) and multiple media (fluid, solid, granule medium, and so on).To establish the geo-material's seepage damage constitutive model, it is very important to introduce and improve the theory advantage of damage mechanics, as well as consider the effect of saturated water simultaneously. Therefore, the principal results obtained in this thesis are listedbellows:1,The finite-strain theory for isotropic elasto-plastic damage solids was presented and developed based on the research work done by the predecessors. Firstly, On the basis of configuration, stress and strain transformation, effective elastic energy, plastic strain increments were analyzed. Then, the coupled constitutive model of isotropic elasto-plastic damage was established and discussed; the evolutional equations and the constitutive equations of damage materials were presented. Finally, the kinematics equation and constitutive equation of damage for finite-strain isotropic elasto-plastic solids were established.2,The theory of isotropic double scalar damage variables was presented on the basis of the research work done by the predecessors. The corresponding strain energy release rate and damage evolutional equations were also drawn. Then the characteristics of isotropic double scalars damage model and its alternative were discussed and analyzed, which made a basis for the contents behind.3,From the point of continuum damage mechanics, the seepage and mechanical characteristics of geo-materials were studied, and the effect Darcy criterion of complete crack media was presented, then the seepage differential equation and the seepage model of porous permeability coefficient evolved was developed. At last, the characteristics of the normal permeability coefficient, the effect permeability coefficient and the effect permeability coefficient of the layer media were discussed and analyzed.4,Combining the theory of continuum damage mechanics and the seepage differential equation presented in this article, the finite element program EPDAP_S , EDAP_D and EDAP_L for the coupled seepage and damage were written using the computer language Fortran90 based on the modified theory of Biot. In the finite element programs, the stresses of the destroyed elements or Gauss points were modified and migrated, which promises the rationality and the accuracy of calculation results.5,Using the program EDAP_D, EDAP_L and EPDAP_S which were compiled personally, the finite element simplified computational model of a soft roadbed foundation was calculated, including the sedimentation, pore pressure, stress, strain, damage, elastic energy and so on. Moreover, the sedimentation and pore pressure of the soft roadbed foundation model was computed for typical nodes. Finally, because it is fuzziness in predicting the properties of soft roadbed foundation due to three time difference schemes(TDS), the problem was analyzed using the program EPDAP_S in the article, and some valuable conclusions were drawn.