Dynamic Elastic Modulus and Damping Ratio of Unsaturated Red Clay

Abstract

Dynamic modulus of elasticity and damping ratio are two important parameters of dynamic properties of soil. These two parameters were extensively studied in the laboratory. However, there has been little research on these two parameters of the unsaturated red clay which is located in the southwest of Hunan, China. With the rapid development of high-speed railway in China, it is urgent to identify the dynamic properties of the unsaturated red clay to provide reference for the civil engineering industry. In this paper, DDS-70, an electromagnetic type dynamic tri-axial testing system, was used to study the effects of water content, dry density, confining pressure, over-consolidation ratio and loading frequency on dynamic elastic modulus and damping ratio of unsaturated red clay. The result shows that within the phase of small strain the influences of water content, dry density, confining pressure, over-consolidation ratio and loading frequency on dynamic modulus of elasticity are obvious. Dynamic modulus of elasticity increases with the increase of dry density, confining pressure and over-consolidation ratio under the same strain, whereas dynamic modulus of elasticity decreases with the increase of water content and loading frequency. Moreover, the effects of these factors on damping ratio are also significant during the phase of small strain. With the increase of strain, damping ratio increases with the decrease of dry density, confining pressure and over-consolidation ratio under the same dynamic strain. There is no clear relationship between damping ratio and loading frequency. It is concluded that the influence of above factors on the dynamic modulus of elasticity and damping ratio is significant.