Disk Transducer for stiffness measurement on granular materials

Small-strain stiffness is one of the prominent characteristics of geo-materials on analysis of deformation behavior. Elastic wave measurement technique is becoming stronger non-destructive tool than other technique. In this paper, authors have focused on the application of the flat surfaced transducer ‘Disk transducer’, enabling to measure both compression and shear wave on triaxial specimen. Disk transducer was built the University of Tokyo using piezo- ceramic element and encapsulated in the top cap and pedestal of small scaled triaxial apparatus then performed the tests. This paper presents the results of three sorts of granular materials, fine, medium and coarse sand, were investigated statically and dynamically at isotropic and anisotropic stress states in the laboratory. The elastic parameters obtained on the granular materials; Young's modulus (E) and shear modulus (G), obtained by statically and by means of disk transducer method were examined and compared. It was observed, the statically and dynamically obtained results are mutually comparable and in agreement with previous studies. It is also confirmed the elastic parameters are to be a unique function of stress states with experimental evidence.