Evaluation of the small-strain shear modulus using two bender-receivers and a controlled external source

The main objective of:this work is to propose a testing system composed by a conventional array of bender elements in combination with a resonant-column apparatus to measure the shear modulus. This system allows the use of the bender elements as receivers while the oscillator of the resonant-column device produces a single burst sinusoidal wave which propagates down across the top cap and soil specimen. The top and bottom bender elements record the movement including the first peak and the free vibration of the system. The travel time is obtained from the delay between both records. Simultaneous recordings of the specimen top rotation are useful to compute the soil shear strain level and to estimate the flexural displacement of the benders. In addition, the relationship between displacement and voltage output is studied. Undisturbed and reconstituted samples are tested with this configuration and the results are compared with the conventional resonant-column test in order to analyze the performance fails test method. Tests with different frequency and amplitude of the single pulse are carried out to check the influence of these parameters on the final result. Results show a good agreement with the conventional resonant-column test at very small-strain showing adequate repeatability and easy identification of the travel time.