Compressive properties of some Swedish and Danish structured agricultural soils measured in uniaxial compression tests

Soil compaction is recognized as a threat to long-term productivity of agricultural soils and as a cause of environmental problems such as flooding. The use of models to establish strategies for prevention of soil compaction is hampered by lack of model input parameters describing soil mechanical properties. This paper presents the compressive properties N (specific volume at sigma = 1 kPa on the virgin compression line), C-c (compression index) and C-r (recompression index) obtained from uniaxial compression testing of 69 individual soil layers and investigates the relationships between these properties and readily quantifiable soil parameters. No correlation was found between compressive properties and soil texture. Instead, N, C-c and C-r were positively correlated to the initial specific volume (v(0)). This suggests that compressive properties are more strongly affected by soil structure than by soil texture. Dependency of compressive properties on v(0) could not be expected from classical soil compressive behaviour theory but suggests modifications to the theory of soil unloading-reloading behaviour. We suggest that the latter is dependent on time between unloading and reloading.