Influence of static and cyclic loading including spatial variation caused by artificially vertical holes on changes in soil pore function, gas transport and hydraulic properties
Soil compaction is regarded as one of the most serious problems resulting in soil degradation in modern agriculture. The overuse of machinery (an increase in weight and frequency of wheeling) has been identified as the main reason contributing to soil compaction. Soil structure has a major influence on the ability of soil functions (e.g. soil aeration and water transport). Therefore, in this study, we hypothesized that soil compaction under static and cyclic loading and the amelioration of soil structure by artificially drilled vertical holes can obviously affect soil physical properties. To better understand the interaction between soil physical properties and the stress-strain behavior as well as their influence on pore functions, soil aeration and gas fluxes, the capacity (total porosity and air-filled porosity εa) and intensity (pore continuity C2-Index and tortuosity τ, air permeability Ka and gas diffusion coefficient Ds/Do) properties of pore functions were investigated. Repacked, homogenized soils (bulk density of 1.4 g cm-3) with three different textures (sand, silt loam and clay loam) at two matric potential (-60 and -300 hPa) under two types of loading (static and cyclic loading) and three compaction levels (50, 100 and 200 kPa) were analyzed. Plastic soil deformation is a reaction of soil to applied stress, if the internal soil strength is exceeded. Mechanical or hydraulic processes can either cause it, while the extent of soil deformation depends on the external stress/internal strength ratio. Therefore, vertical displacement and pore water pressure were also detected by our experiment.
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