ABSTRACT

A reactive soil is one which exhibits volume changes as a result of changes in moisture content. Soils swell in response to an increase in moisture, and shrink in response to a decrease. There are three components to the consideration of the effect of reactive soils: the soil profile, the moisture changes which occur in the soil, and the type of building which is placed on the site. Some care is required in assessing the soil profile. Moisture changes in near surface soil layers occur on a cyclic basis as a result of seasonal variations in climatic factors. However, other human influences are also important. The loads imposed by a typical residential house are well below those which would be necessary to inhibit swelling, and no surface footing can restrict shrinkage of the foundation soil. Surface movements are a cumulative effect of all the different layers of soil within the depth of soil affected by moisture content/suction changes.