Low‐Stress Dilation Test

A new test to measure the low‐stress dilation behavior of cohesionless soils subjected to plane strain has been developed. Very large strains (30–35%) have been applied to sand specimens while approximately maintaining the parellelopiped shape of the specimen. A small version of the apparatus designed to test sands is described. However, it should be relatively easy to construct larger devices with the potential for testing rockfill‐like materials. A model approximating the effect of initial density on dilation behavior is presented that suggests a method for defining and measuring index void ratios that are intrinsically related to dilation behavior. The ultimate constant volumetric strain void ratio for low‐stress plane strain was found to vary with the initial void ratio of the specimen. The effect of fabric anisotropy on dilation behavior has been studied and modeled. A dilation test on sand‐cement shows that contact cohesion increases the rate of dilation of a loose sand to the rate expected for an uncemented dense sand.