Microcomputer Based Free Torsional Vibration Test

Abstract

A microcomputer based free torsional vibration testing system is introduced; its ability to determine the shear modulus and damping ratio of soils is demonstrated. In comparing with the resonant column method, the free torsional vibration testing system seems to offer reliable results, less expensive instrumentation, easier and faster operation, and less disturbance to soil specimens. The system also offers the advantage of conveniently studying the effect of a number of parameters, such as the initial shear strain and cycle number on the dynamic modulus of soils. This nondestructive testing system may also be used effectively in the determination of dynamic response of compacted clay soil. The measured maximum shear modulus appears to relate closely to the structure of clay particles and the stiffness of the soil specimen. On that basis, the free torsional vibration test might be used to identify the fabric related stressstrain behavior of both sand and clay with little disturbance to a specimen.