Quantification of the soil pore network by 3D image analysis: three different approaches

X-ray micro-tomography in the last decade has become the most widely used tool toobtain 3D images of the pore network of undisturbed soil samples. The successivelogical goal is the effective quantification of the pore space in order to link structuralproperties to soil functions, including water flow and solute transport processes.The pore network of two very different soil samples has been reconstructed usingthe x-ray desktop microtomograph Skyscan 1172 and the comparison of three differentapproaches of 3D image analysis has been done. The classical objects orientedimage analysis approach has been compared with the pore-throat analysis based onthe medial axis transform proposed by Lindquist and Venkatarangan (2000) and thesuccessive opening algorithm (Serra, 1982) based on mathematical morphology. Thethree pore measurement procedures provide very different results in terms of physicalmeaning. The first one seems more suitable to identify soil pore genesis due to itspossibility of accurate quantification of pore shapes. The pore-throat analysis showsstrong linkage with behaviour of fluids in the pore network while the successive openingalgorithm has allowed good interpretation of water retention properties. Differencesalso in terms of computation efficiency have been pointed out using a graphicworkstation having two processors dual core with 8Gb RAM.