Calibration Exercise of Fixed-Free Resonant Column Apparatus

Abstract

In this paper, the conventional calibration exercise for resonant column apparatus has been re-examined and some recommendations were provided to improve the accuracy of the test results. During the testing, specimen is assumed to be fixed at bottom and dynamic torsional vibrations are applied at the top using drive system consisting of four magnets. Due to complicated geometry of the drive system, its mass polar moment of inertia (Jd) is found to be difficult to estimate. So, calibration exercise is performed to determine Jd. In this present study, calibration rods of aluminum of known stiffness were used. The diameter of each aluminum rod was varied from 8 to 15 mm and keeping the constant height of 100 mm. The study revealed that the mass polar moment of inertia of the resonant column system is frequency dependent. Also, the solid cylindrical sand specimens were tested using resonant column tests and bender elements tests with varying confining pressure and relative density.