Modelling of curling in desiccating clay

Abstract

This paper investigates the significant curling that occurs when thin soil layers undergo desiccation. Curling deformations, in the form of (1) lifting off from the edges (generating a concave surface), or (2) lifting off from the middle (creating a convex surface), are reported in the drying of soft soil and concrete pavements in the field. This paper presents experimental observations of significant curling of both forms 1 and 2 in wet soil specimens under controlled drying conditions. A theoretical explanation for curling is presented on the basis of unsaturated soil mechanics. The curling was primarily attributed to differential shrinkage strain increments that occur down the soil profile and their variation with the progression of desiccation. Making use of nonlinear elasticity theory under large deformations and measured properties, the shrinkage and curling deformations were modelled using the FLAC (Fast Lagrangian Analysis of Continua) computer program. The modelling approach appears to capture the observed behaviour of curling during desiccation.Key words: shrinkage, clay, curling, suction, desiccation, moisture migration.