Design and Performance of Mat Foundations on Expansive Clay

Abstract

A design procedure for stiffened mats on expansive clays has evolved over the past seven years and it has now been applied successfully on two continents in areas where expansive clay damage had previously been severe. The core of the design approach recognizes that soil support offered by differentially expanding and shrinking clay is influenced mainly by the changing moisture regime beneath a mat and then natural gilgai form of expansive clay deposits. Empirical coefficients developed from a series of beam- and stiffened plate-on-mound computer analyses relate the predicted soil behavior to mat design quantities. The design procedure was applied to the design of school building foundations in Australia and field performance has been observed for over two years. The predicted soil movements were matched accurately by those observed and despite their magnitude, the mats have performed satisfactorily.