Resonant column and bender element tests on maximum shear modulus of dry sand

The problems and solutions of applying the bender element method to determine the maximum shear modulus(Gmax) of sand are investigated by conducting resonant column(RC) and bender element(BE) tests on four dry sands obtained from Germany.The study indicates that the start-to-start method is more reliable to identify the time of shear wave propagation in specimens compared to other methods.In BE tests,the excitation frequency of input waves has influence on the tested Gmax,and this influence is dependent on soil types and reduced by increasing confining pressure.A comparison between RC and BE tests shows that Gmax by both methods may be well expressed as a linear equation;for the Berlin sand and Braunschweig coarse sand,there exists a threshold Gmax below which Gmax by BE tests(Gmax(BE)) is greater than that by RC tests(Gmax(RC)),however beyond which the Gmax(BE) is smaller than Gmax(RC) and the distance between both increases with increasing stiffness soil.In practice,it is suggested that the input voltage with proper high frequency is preferred for BE tests,as compared with RC tests.