On computational homogenization of transient poromechanics problems

Sammanfattning: Road pavement deteriorates gradually under the combined influence of traffic load from moving vehicles and climate-induced effects, such as moisture. By means of numerical simulation, we can increase our understanding of this physical phenomena, allowing for an improved pavement design with prolonged service life. Asphalt concrete, the most commonly used material for road pavement, is a highly heterogenous porous material consisting of asphalt (bitumen) binder and particulate construction aggregates. The current simulation methods either model the material with pre-calculated effective material properties, i.e. a priori homogenization, or discretize the spacial domain to a very fine extent in order to capture the complex interaction between the matrix and inclusions. The former approach is based on particular assumptions and cannot provide a general solution, while the latter is computationally too expensive. This thesis is engaged in developing a competent computational model for numerical simulation of such heterogeneous materials. A multiscale modeling framework based on generalized macro-homogeneity condition is proposed for the analysis of a class of quasistatic problems relevant to the deformation and seepage in two-phase porous media. Within this framework the classical approach of first order homogenization for stationary diffusion problems is extended to transient problems in a consistent manner. Homogenization is carried out on Representative Volume Elements (RVE), which are introduced in quadrature points of the macroscale elements in the spatial domain. The corresponding algorithm is thus of a nested character (FE^2). The proposed strategy is applied to the transient and nonlinear problem of consolidation of asphalt concrete road pavement. In particular, the degree of scale separation, i.e. the choice of RVE size, is investigated. The influence of inclusion distribution inside the RVE and the size effect of the inclusions are also examined. Furthermore, different decoupling strategies are considered.