EFFECT OF BOUNDARY CONSTRAINS ON DESICCATION CARCK OF SWELLING SOIL

Swelling soil is a special soil often encountered in geotechnical engineering. It is of classic drying shrinkage and water swelling characteristics due to the moisture change in soil. How to quantify the shrinkage deformation and its relationship with desiccation crack is important issue in assessment of the stability and security of earth structures. The analysis based on distribution of water content is proved to be equivalent of that base on matric suction by Bishop's effective stress and generalized Hooke's Law. The shrinkage coefficient measured by shrinkage test of undisturbed soil sample can be associated with shrinkage strain. The total horizontal stress and its relationship with the distribution of water content is obtained with or without consideration of boundary displacement constrains. The results show that the non-uniform of shrinkage deformation and stress level is small and little desiccation cracks will be produced when there are no boundary constrains in soil. But if the displacement constrains are imposed at the ends of soil body, shrinkage deformation can be restrained and desiccation cracks can be produced. The depth of desiccation crack is strongly influenced by Young's modulus and shrinkage coefficient of soil.