The Design of Residential Foundations on Expansive Clays

Summary Damage to residential buildings resulting from expansive clay movements, thatb is shrinkage and swelling caused by changes in sub-soil moisture, has been recorded worldwide. Previous methods for the design of footing systems to minimise distortion and cracking in buildings constructed on expansive clays have been based on highly idealised analytical design models. Due to the extreme variability of soil profiles and the complicated nature of the problem,analytical models fail to accurately model the behaviour of expansive soils encountered in the field.In an attempt to provide a more reliable and rational design technique, this paper concentrates on the development of a probabilistic technique for the design of residential foundations on expansive soil based on an extensive database of current footing designs and their performance in the field. This will enable the degree of risk (or probability of encountering damage) associated with current footing designs to be quantified,for example,by means of design charts. By formulating a method of footing design in which both the home owner and engineer understand the
consequences of their decisions, it is hoped that the occurrence of future litigation in this field will be minimised.
Also, designs will be based on a more sophisticated approach,that is, on footings constructed and tested in the field under a variety of environmental conditions.