The role of lateral stresses on soil water relations in swelling clays

The moisture characteristic of a swelling soil is the result of complex interaction between the soil water potential and imposed mechanical stresses. This can give rise to soil water profiles which cannot be interpreted by soil water theories for non-swelling soils. Agricultural soil physics has been concerned primarily with highly structured surface soils, and has developed simple theories for the effects of stress on soil water relations in swelling soils. These simple theories ignore the effect of lateral stress in the soil. Civil engineers, on the other hand, dealing mainly with less complex soils at depth, have developed more complex theories for the effect of three-dimensional stress states on soil water relations. This paper shows how the effect of three-dimensional stress can and should be included in soil water studies of swelling soils, and gives examples to demonstrate the possible magnitude of such effects.