Two Bender Receivers Frequency Domain Analysis in Resonant Column Tests

The installation of bender elements (BE) in different geotechnical testing devices has been increasing in recent years. One of the most widespread combinations in this matter is the use of BE in resonant-column (RC) equipment. Taking into account that the piezoceramic elements can work alternatively as a transmitter or as a receiver, a complementary testing procedure is proposed by using the same RC-BE device. In this case, the perturbation signal is produced by the RC oscillator, while the response of the system is measured by the pair of BE located at each end of the specimen. The analysis of the received data by use of frequency domain techniques allows the dynamic properties of the soil specimen to be obtained. An RC apparatus capable of producing and transmitting a signal with a specific frequency band (i.e. sine sweep or random noise) was equipped with BE and software designed to perform this type of combined tests (TRFD). A laboratory test programme of RC and TRFD combined tests was conducted in order to study the feasibility of this hybrid method. Results indicate that the method could be useful as a complementary tool to evaluate the small-strain stiffness of soil when performing RC and BE tests.