Effects of trafficking by heavy agricultural machinery on mechanical and structural properties of restored soil

Abstract

More and more fertile agricultural soil is temporarily excavated and later restored. In order to study the mechanical stability of a soil that was restored according to current regulations, we conducted two traffic experiments (2 and 10 passes) in two subsequent years on a soil which had been restored 4 years prior to the beginning of the experiments. Whereas 2 passes mainly reduced coarse porosity, 10 passes decreased coarse porosity even strenger and also changed the mechanical properties and macro-pore structure. Precompression stress was increased, while the slope of the virgin compression line was decreased. This latter effect may be related to the convention that moisture conditioning of the samples relates to water tension (field capacity) and not to water content. Visualization by computed tomography revealed that larger macro-pore spaces were more affected during compaction than smaller ones. The remaining macro-pores were much less interconnected than without trafficking. In summary, although the soil had partially regained mechanical strength within 4 to 5 years after its restoration, it still remained susceptible to compaction.