Laboratory study on small-strain dynamic properties of sand by bender-extender element

Measurements of small-strain dynamic properties by bender elements are popular in recent years. However, the study of bender-extender elements is less mentioned, and their application in China has rarely been reported. In this study, the S-wave and P-wave velocities of Fujian sand are simultaneously measured by a single pair of bender-extender elements. In order to find the travel time for S-wave and P-wave, wider excitation frequencies and different methods are used, and reliable methods for the determination of the S-wave and P-wave velocities are obtained. The test results show that the peak-peak method and the cross-correlation method using 10~20 kHz excitation frequencies are exact and convenient. The small-strain properties, including shear modulus G₀, constrained modulus M₀ and Poisson's ratio υ, are determined for specimens by measuring the S-wave and P-wave velocities. G₀ increases faster than M₀ as the soil density and confining pressure increase. The Poisson's ratio decreases linearly with the increasing soil density and confining pressure. The results of this study provide effective methods for the further application of bender-extender elements.