No abstract

The shrinkage geometry of a clay soil drying from saturation to oven dryness was investigated. Undisturbed samples in rings measuring 232 cm3 were taken in the field at depths of 0.0, 0.20, 0.40 and 0.60 m. Overburden pressures at these four depths were determined by wet bulk‐density determination. Samples were oven dried with various loads applied on top. Surface subsidence and total volume decrease after drying were measured. It appeared that, for each soil layer, shrinkage at overburden pressures equal to or larger than field pressures was isotropic. When the load was removed during drying, subsoil samples showed relatively large cracking in comparison with surface subsidence.

No abstract

Field studies on swelling and shrinkage in clay soils are scarce, due to the lack of sound experimental methods and suitable mathematical equations. This study was aimed at developing such methods and equations. Disks were positioned at various depths in the soil in order to measure vertical movements in undisturbed soil. Newly developed equations were applied to convert these vertical soil movements into three‐dimensional volume changes and crack volume and to relate them to water‐content changes. These equations are unique in that they are valid for water loss in the structural‐, normal‐, residual‐, and zero‐shrinkage phases, and for both isotropic and anisotropic shrinkage. Methods and equations were successfully tested in a 1‐yr field experiment in a heavy marine clay soil in the Netherlands. The use of seven rotating disks for measuring soil volume changes was about 10% more accurate than two other less laborious methods. An interesting application of this method and equations is the determination of soil water‐content changes by measuring vertical soil movements.

No abstract