ImageBased Analysis of Pore and Particle Structures
The goal of this project is to develop an analysis environment for highresolution CT scans of porous materials. This environment will integrate methods to compute the topological structure of the pore space and use image processing algorithms as well as geometric algorithms to exactly assess geometrical properties. Furthermore, the characteristics of the extracted structures will be investigated and determined. The visualization software Amira provides the framework for the analysis tools.
Background
Particle Structure
Pore Structure
The segmentation results also provide a basis for analyzing the pore space. Interesting elements of the pore space are pores, pore paths and pore constrictions. These elements can be described by the topology of the distance transform containing the distances to the boundaries of the segmented particles. The elements of the pore structure and other parameters e.g. radii can be extracted from CT data and used to construct a graph representing the pore space. Here, we apply a Voronoilike approach to obtain these structures [Homberg et al. 2012]. The idea is a watershed propagation of the labeled particle regions based on the distance transform. The pore graph is constructed from all points of cell boundaries with at least three adjoining particle regions. This approach allows us to represent the topology of the pore space by a compact pore graph. To extract the pore bodies, again, we apply a watershedbased method marked by the extracted pore centers of the pore graph. These results, in turn, can be used to derive parameters (pore constriction distribution, connectedness quantities) for simulating suffosion processes.
The constructed pore graph allows us to use this compact representation for an efficient analysis of transport possibilities. We apply a method that successively blocks the critical percolation edges in order to determine sizedependent transport possibilities. Here, an iterative mincut adaption filters the maximal radius that holds the topbottom connection and finds and cuts the edges of that radius which particles have to pass. The described process computes a decomposition of the pore graph into a topsubgraph and a bottomsubgraph connected by the critical edges in each iteration. These results can be used to estimate a sizedependent cumulative number of possibilities as well as an upper bound of the largest mobile particle.
Publications
2018 

Feda Seblany, Ulrike Homberg, Eric Vincens, Paul Winkler, Karl Josef Witt  Merging criteria for defining pores and constrictions in numerical packing of spheres  Granular Matter, 20(37), 2018 (preprint available as ZIBReport 1825) 
PDF (ZIBReport)
BibTeX DOI 
2017 

Feda Seblany, Ulrike Homberg, Eric Vincens, Paul Winkler, Karl Josef Witt  Merging criteria for the definition of a local pore and the CSD computation of granular materials  Proceedings of the 25th meeting of the Working Group on Internal Erosion in embankment dams and their foundations, pp. 150159, 2017, isbn: 9789082746815  9789082746808 (preprint available as ZIBReport 1809) 
PDF (ZIBReport)
BibTeX 
2015 

Eric Vincens, Karl Josef Witt, Ulrike Homberg  Approaches to Determine the Constriction Size Distribution for Understanding Filtration Phenomena in Granular Materials  Acta Geotechnica, 10(3), pp. 291303, 2015 (preprint available as ) 
BibTeX
DOI 
2014 

Ulrike Homberg, Daniel Baum, Alexander Wiebel, Steffen Prohaska, HansChristian Hege  Definition, Extraction, and Validation of Pore Structures in Porous Materials  Topological Methods in Data Analysis and Visualization III, pp. 235248, PeerTimo Bremer, Ingrid Hotz, Valerio Pascucci, Ronald Peikert (Eds.), Springer, 2014 (preprint available as ZIBReport 1356) 
PDF (ZIBReport)
BibTeX DOI 
2012 

Ulrike Homberg, Daniel Baum, Steffen Prohaska, Ute Kalbe, Karl Witt  Automatic Extraction and Analysis of Realistic Pore Structures from µCT Data for Pore Space Characterization of Graded Soil  Proceedings of the 6th International Conference on Scour and Erosion (ICSE6), pp. 345352, 2012 
BibTeX

2011 

Ulrike Homberg, Daniel Baum, Steffen Prohaska  Describing and Analyzing the Dual Structures of Porous Media  Proc. 3DMicrostructure Meeting, Frank Mücklich, Philipp Slussallek, Katja Schladitz (Eds.), pp. 2425, 2011 
BibTeX

2010 

Richard Binner, Ulrike Homberg, Steffen Prohaska, Ute Kalbe, Karl Josef Witt  Identification of Descriptive Parameters of the Soil Pore Structure using Experiments and CT Data  Proceedings of the 5th International Conference on Scour and Erosion (ICSE5), pp. 397407, 2010 
BibTeX

2009 

Olivier Semar, Richard Binner, Ulrike Homberg, Ute Kalbe, Tobias Mehlhorn, Steffen Prohaska, Volker Slowik, Karl Josef Witt  Conditions for Suffosive Erosion Phemomena in Soils – Concept and Approach  Workshop Internal Erosion, pp. 2935, Vol.21, Schriftenreihe Geotechnik, 2009 
BibTeX

Ulrike Homberg, Richard Binner, Steffen Prohaska, Vincent J. Dercksen, Anja Kuß, Ute Kalbe  Determining Geometric Grain Structure from XRay MicroTomograms of Gradated Soil  Workshop Internal Erosion, pp. 3752, Vol.21, Schriftenreihe Geotechnik, 2009 
BibTeX

Tobias Mehlhorn, Steffen Prohaska, Ulrike Homberg, Volker Slowik  Modelling and Analysis of Particle and Pore Structures in Soils  Workshop Internal Erosion, pp. 5360, Vol.21, Schriftenreihe Geotechnik, 2009 
BibTeX
