Laboratory Investigation of Desiccation Cracking

Abstract

Shallow slope failures occur frequently in roadway cuts and on embankments along Oklahoma highways. Slope failures in clayey soils are often preceded by periods of drying and formation of desiccation cracks followed by significant precipitation events. Desiccation cracks have a significant impact on slope stability as they allow water to rapidly penetrate the soil, which accelerates softening and shear failure in shallow layers. To better predict the stability of shallow slopes in clayey soils it is important to fully understand the mechanics of desiccation crack formation. In this paper, the desiccation behavior of clayey soils is described as a function of moisture content and soil suction based on preliminary results obtained using a bench-scale apparatus to study desiccation crack formation. An innovative device was developed to determine tensile stresses during crack development while monitoring moisture content changes and crack formation via time lapse photography. This paper presents the preliminary results of the bench-scale studies of desiccation cracking in soil obtained from two test sites in Oklahoma. It was found that the peak tensile stress occurred when the initial crack appeared on the soil surface at the early stage of drying. The results also show that the tensile strength increased with increase in dry unit weight and that specimens compacted to 2% wet of optimum resulted in higher strength than those compacted to optimum moisture content.