Structural Heterogeneity of Soil Clods : Correlating Weibull Parameters to Fracture Surface Topography
Planes of weakness (i.e. cracks) existing in the soil matrix propagate creating fracture surfaces and fragmenting the clod into smaller clods. The fracture topography (i.e. roughness) as the macropore surface area has important consequences from carbon turnover to mass exchange processes during preferential flow episodes. However, it is widely unknown how the distribution of cementing agents (i.e. organo-mineral compounds) affects the topography of fracture surfaces since cracks tend to propagate around contact points with higher bonding strength. The objective was to investigate the Weibull modulus of clod tensile strength as a quantifier of fracture surface topography resulting from the clod breakage. Therefore, a tension testing machine was constructed that allowed defined indirect tensile strength tests. A total of 280 clods of 4 size-classes from two contrasting soils were considered: The Bt horizon from Haplic Luviso with finer texture and organic-mineral coatings and the C horizon from Haplic Regosol with coarser texture and less organic-mineral coatings. The structure of Bt-clods presented a higher heterogeneity of organo-mineral coating distribution compared to C-clods. The crack propagation on a heterogeneous structure resulted in a straight fracture surface. However, on a more homogeneous structure, crack propagation produced a more crooked fracture surface, with higher roughness. Cylindrically shaped clod standardisation allowed to capture the clod structural heterogeneity by the Weibull modulus of tensile strength. In hierarchical soil structure, a scale effect was observed on the Weibull modulus of clod tensile strength and fracture surface roughness that decreased when increasing clod size. Moreover, an exponential relationship between the Weibull modulus and fracture surface roughness was found
Year of publication: |
[2022]
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Authors: | Pires Barbosa, Luis Alfredo ; Gerke, Horst H. |
Publisher: |
[S.l.] : SSRN |
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