Precise observation of soil surface curling

Abstract

The process of drying in soil is often associated with complex deformations. Due to the complexity of both the soil structure and the coupled hydro mechanical processes occurring during drying, different forms and shapes can be created during drying. Soil curling is recognized as one of the typical phenomena taking place during shrinkage, when the surface layer is curled up or down by different mechanisms triggered during drying. A precise non-contact electro-optical technique based on a 2D laser profile scanner with motion controller to systematically track the evolution of the exposed surface of a natural soil during controlled drying conditions was used in this research. Different stages of curling were identified at different elapsed times. These stages are discussed in detail. To gain a better understanding of the different curling stages and their associated mechanisms, a set of drying experiments were performed on artificially prepared mixtures of kaolin and silica sand. Particularly, two basic mechanisms were studied: differential drying and differential shrinkage effects. A simple conceptual model is also proposed and discussed to help in the interpretation of the test results involving the curling.