Disk shaped piezo-ceramic transducer for P and S wave measurement in a laboratory soil specimen

Piezo-ceramic elements are customized as transducers for the measurement of mechanical properties of materials in the engineering field. This was made possible with the industrial production of piezo-ceramic elements in various shapes and sizes. This paper describes the development of a single flat disk shaped piezo-ceramic transducer for measuring both compression and shear wave on an identical soil specimen. Procedures for interpreting results, initial verifications of its performance and applications are also presented. Two types of piezo-ceramic elements, one for measuring P waves and the other for S waves, were placed together in a metal housing, which worked as a wave measuring transducer installed in a triaxial apparatus. Three kinds of granular geo-materials, fine, medium-coarse and coarse sands, were tested. Small strain shear stiffness, G_max, of the tested sands was evaluated by various techniques, including proposed disk transducer method, trigger and accelerometer method and traxial small strain cyclic loading. Shear moduli obtained from all the techniques fell in a similar range within allowable scatters and it was confirmed that the disk transducer was one of applicable wave measurement technique for laboratory soil specimens.