On the performance of bender elements in triaxial tests

This paper presents the results of a research programme in which the transfer functions of bender element/soil systems have been measured for various materials, setups and stress levels. The resulting database has allowed the characterisation of the inherent multi-vibrational nature of the system, and the interpretation challenges that this imposes. The excitation of multiple modes of vibration may introduce signal distortion and consequently differences between group velocity and phase velocity. This means that the common assumption of conventional interpretation techniques that group velocity is equal to shear-wave velocity is in error. Based on the features observed, system parameters have been introduced and a parametric analysis carried out in order to assess the performance of the system and to better understand the effects of multimodal vibration as an attempt to improve signal interpretation.