Quantitative 3D-fracture analysis by means of microfocus X-ray computer tomography (mu CT): an example from coal

Since the introduction of medical computer tomography (CT) in geological sc iences, many applications have been worked out. However, its limited resolu tion (optimal 60 x 60 x 1000 mum(3)) restricts its general use. Enhanced re solution is achieved with synchrotron X-ray tomography, but these instrumen ts are expensive and have a limited access. Another technique is microfocus X-ray tomography of which the advantages will be discussed. This instrumen t is more accessible than synchrotron facilities. It furthermore has a supe rior resolution (present-day 10x10x10 mum(3)) compared to medical CT. In th is study, a thorough calibration is performed on samples of 8 mm in diamete r and fracture widths from 0 to 400 mum. A statistical evaluation shows tha t the beam hardening artefact can be neglected and the standard deviation o n aperture measurements of 100 mum is about 15 mum. The application of quan titative fracture aperture analysis will be demonstrated on a coal sample w hereby a good correlation (r=0.94) with fracture analysis by reflected ligh t microscopy is illustrated.