Volumetric shrinkage characteristics of soil during drying

Drying shrinkage is one of the intrinsic characteristics of soil, and has profound effects on its engineering properties. In this investigation, laboratory tests are conducted on initially saturated paste-like specimens and compacted specimens with different compaction parameters. For the paste-like specimens, the fluid volume displacement technique is employed to measure the volumetric change of specimens during drying, and the complete shrinkage curve is determined. It is found that three stages can be distinguished in the shrinkage of paste-like specimens, namely normal shrinkage, residual shrinkage and zero shrinkage; most of the volumetric shrinkage deformation occurs before the air-entry point while the soil is still fully saturated; the volume shrinkage behavior and shrinkage curve shape significantly depend on soil microstructure characteristics. For the compacted specimens, the shrinkage behavior is significantly controlled by the initial drying density and water content. In general, shrinkage strain decreases with the increase of the initial dry density and increases with the increase of the compaction water content. In addition, the results show that the shrinkage of compacted specimens is anisotropic rather than isotropic, and is more sensitive to the initial water content than the initial dry density. A coupled linear and exponential equation is finally developed from the obtained data to describe the shrinkage strain at the given initial drying density and water content.