Evaluation of Transfer Function and Dynamic Properties from Strain-Controlled Resonant Column Tests

Abstract

Abstract Dynamic properties of soils can be inferred via curve fitting of the transfer function between the excitation and the induced strain using a resonant column device. The shape of the measured transfer function is distorted and differs from that of the theoretical transfer function because of different shear strain levels at different frequencies in the specimen. The difference becomes more pronounced with increasing shear strain levels. This study presents a new methodology for the evaluation of dynamic properties from an improved transfer function. In this methodology, the soil specimen is excited using a sinusoidal carrier excitation at the desired strain level coupled with simultaneous excitation of a very small strain random noise. The desired strain level induced by the fixed sine controls the resonant frequency of the specimen, whereas the small strain random noise (always kept small) determines the shape of the transfer function and thus the damping coefficient. The results indicate excellent matching of the transfer function obtained from the proposed method and the theoretical transfer function at all shear strain levels. The new methodology also shows good potential for the evaluation of dynamic properties of soils as a function of frequency in resonant column testing.