Influence of Horizontal Stresses on Gilgai Landforms

Abstract

Gilgai landforms are series of mounds and depressions with amplitudes that range from 7.6 to 45.7 cm (3 to 18 in.) and wavelengths that range from 4.6 to 9.1 m (15 to 30 ft). Gilgai landforms occur in soils parented from overconsolidated expansive clays in Texas. A mechanism is proposed that may be causing these landforms and undulations in pavements. The presence of naturally occurring horizontal stresses in overconsolidated expansive clays is believed to be the essential cause of these extreme movements. It is proposed that the horizontal stresses alter the normal vertical stresses in a prebuckling mode and produce a differential vertical rebound. The behavior of gilgai and their associated shear fractures support this theory.