Compaction bands in Tuffeau de Maastricht: insights from X-ray tomography and multiscale modeling

We present a study on compaction band in a high-porosity limestone (Tuffeau de Maastricht) based on comparison and analysis of X-ray tomography observations and computational multiscale simulations. We employ a hierarchical multiscale approach coupling the finite element method (FEM) with the discrete element method (DEM) to simulate the formation of compaction bands in Tuffeau de Maastricht. A high-porosity RVE is prepared according to X-ray tomography observations of material microstructure, and its grain-scale parameters are calibrated by data from laboratory isotropic compression and triaxial compression tests. Triaxial compression tests are simulated by FEM as a boundary value problem to observe compaction bands. The generated RVE is embedded into each integration point of the FE mesh, receiving displacement gradient as DEM boundary conditions, and is solved accordingly to produce the required mechanical responses for FEM computation without assuming phenomenological constitutive relations. The simulated global mechanical responses of the triaxial tests are found to show qualitative agreement with the experimental data. The evolution of compaction band patterns in the simulation matches remarkably well with the experimental observations in terms of fields of porosity and incremental strains. Both show two compaction fronts initiating from the two ends of the specimen and propagating toward the middle. By virtue of the multiscale approach, useful microstructural information is further extracted from the simulations to offer cross-scale insights into compaction bands. The study confirms that significant debonding accompanied by collapse of macropores and grain rearrangements is the major microstructural mechanisms causing the formation of compaction bands in high-porosity Tuffeau de Maastricht.