Stress–strain effects in structured unsaturated soils on coupled mechanical and hydraulic processes

The stress–strain processes in structured unsaturated arable and forest soils depend very much on the internal soil strength and on the existing hydraulic and mechanical boundary conditions. These variables affect soil deformation by compaction and shearing to a great extent. As soon as the internal soil strength, defined as the precompression stress value, is exceeded by external forces, an intense virgin compression process occurs in combination with shearing forces at high pore water pressure values. These processes result in a complete homogenisation of the soil profile down to a certain depth. Consequently, both the hydraulic and the gas fluxes are affected, which results in an intense alteration of ecological and mechanical properties of the site. The consequences of such compaction and shearing on soil strength and on sustainable land use must be considered with respect to the sustainability of the system.