Correlations between Geotechnical Properties and the Swell Behavior of Compacted Shales

Because of the large quantities of shale in Kentucky, numerous highway embankments have been constructed using compacted shale, and many roadway cuts have been made of shale. When exposed to environmental moisture, shale tends to degrade and swell. As a result of this degradation, embankments and subgrades constructed from compacted shale will experience excessive settlement or a reduction in stability. Although this degradation may occur over a long period of time, the experienced settlement and loss of stability can lead to costly maintenance requirements. Laboratory tests such as slake durability and swell testing can be used to define parameters useful in predicting such behavior. This paper presents the results of swell and durability testing performed on unweathered core samples of shale. It was observed that the free swell is related to the natural water content, and there are correlations between swell behavior and the effective friction angle of compacted shale. It was also found that the ratio of slake-durability index and clay fraction can be used to predict the swell behavior of shale.