A Representative Method on Deformation Properties of Clay Specimen in Axial Symmetric State by Introducing Joint Element

Abstract

When a steel piston is pushed into the specimen of cohesive soil from the surface, the soil surface around the steel piston begins to swell up and a ridge circle is built there. As this range of a ridge circle is seemed to be the non elastic zone, it was intended to describe the non elastic deformation by FEM analysis. For the purpose, a stiffness matrix of joint elements applicable to the condition of the axial symmetry was induced. In the specimen of cohesive soil (elastic body) in the cylindrical vessel, a cap zone of the joint elements was assumed. Actually the cap zone shows a non elastic behavior in loading state. And by adding different initial stresses to the joint element, various patterns of surface deformation can be derived under condition of the axial symmetry. This is the theoretical method to control the pattern of surface deformation.
The experiment was carried out as follows ; the loaming soil was packed in the cylinder mold which was 30 cm in diameter and 12.5 cm high. A steel piston of 5 cm in diameter was inserted in the soil from the center of the soil surface. The surface displacement of the specimen was measured precisely by using non contactive displacement meter. The result of the measurement was in agreement with the result of the cap zone analysis, and thus the validity of the proposed method was confirmed.