By micromechanics of geocomposites, we understand an analysis of mechanical properties of modified geomaterials by numerical testing of digitalized samples with complicated microstructure but known local material properties. We touch several important and interacting topics–numerical upscaling and understanding of its results; application of X-ray computed tomography (CT) for visualization of structure of geomaterials; processing the digital image data for constructing FEM models of test samples; numerical testing of digitalized samples for obtaining homogenized properties and study of sensitivity to changes in local material properties, micro-level structure and FE mesh; validation of numerical results by comparison with laboratory testing of samples; use of identification technique for refining the local material properties and calibration of the upscaling procedure.
We follow a two-scale view on the behaviour of geomaterials. The macro-scale corresponds to the use of material in engineering applications, whereas the micro-scale considers the microstructure with much smaller dimensions of inclusions, grains, cracks etc. The micromechanics then represents an analysis of elastic and inelastic plastic or damage material behaviour based on micro-scale information about the microstructure. We assume that the continuum mechanics models can be used on both scales.
Our aim is to derive the macro-scale properties using the information on microstructure geometry and local material properties. We can call this process as upscaling or homogenization, as the heterogeneous microstructure will not be further visible at the macrolevel. Our computational procedure, shortly described in the sequel, is a numerical analogue to the classical laboratory testing on samples with heterogeneous microstructure and with dimensions proper for getting representative macro-scale behaviour. We shall first describe such computational upscaling for the case of elasticity and later discuss possible extension of such procedure for investigation of inelastic material behaviour including damage.
X-ray computed tomography (CT) is used as asuitable tool for getting information about the geometry of the microstructure and, with some level of uncertainty, about the inner material composition. We shall show that CT scanning can be used for construction of finite element meshes for computational upscaling.
After introduction the basic ideas of analysis of elastic behaviour, we consider questions of uncertainty arising from proper interpretation of CT scans and using the local material properties. Finally, we discuss the questions of simulation of inelastic behaviour and efficient computing.
The suggested procedures are applied and tested on analysis of the behaviour of coal-polyurethane geocomposite arising from coal seam grouting for improving resistance to dynamic events.