Ulrike Homberg

Identification of Descriptive Parameters of the Soil Pore Structure Using Experiments and CT Data

In this paper, methods are presented that combine experimental and micro tomographic information to derive parameters of the grain and pore structure of wide-gradated soils. For this purpose, samples based on a model soil were prepared for special experiments as well as for high-resolution CT imaging. Compacting and column experiments were developed to determine specific parameters of the pore and grain structure. Among others, the grain size and discharge quantity of potentially mobile grains were identified as well as characteristics of the supporting skeleton of the model. The results of the compaction and column experiments provide suitable geometric parameters of realistic grain and pore structures for analyzing suffosive erosion phenomena, whereas the CT specimens support the description and visualization of representative pore structures. The presented methods contribute to a better understanding of the physical processes within the pore structure. As a part of the joint project Conditions of suffosive erosion phenomena in soils, the results of this paper can be incorporated into pore-network models to verify and simulate existing transport models.

Definition, Extraction, and Validation of Pore Structures in Porous Materials

An intuitive and sparse representation of the void space of porous materials supports the efficient analysis and visualization of interesting qualitative and quantitative parameters of such materials. We introduce definitions of the elements of this void space, here called pore space, based on its distance function, and present methods to extract these elements using the extremal structures of the distance function. The presented methods are implemented by an image-processing pipeline that determines pore centers, pore paths and pore constrictions. These pore space elements build a graph that represents the topology of the pore space in a compact way. The representations we derive from μCT image data of realistic soil specimens enable the computation of many statistical parameters and, thus, provide a basis for further visual analysis and application-specific developments. We introduced parts of our pipeline in previous work. In this chapter, we present additional details and compare our results with the analytic computation of the pore space elements for a sphere packing in order to show the correctness of our graph computation.