Comparison of Dynamic Behavior of Reconstituted and Core Barrel Sand Soil Sample by Resonant Column Test in Flexural Mode

Determining the dynamic properties of soils is an important issue in solving seismic geotechnical engineering problems. In this respect, several types of field and laboratory methods are available with different advantages and limitations regarding solving different problems. The difference between the results of in-site and laboratory tests is one of the engineers’ difficulties. Some reasons for the difference between the values of dynamic parameters which achieved from field and laboratory tests, are remolding effect of samples, difference in stress conditions and loss of cementation; negligence to these facts in soil dynamic properties may lead to serious damage due to unrealistic soil analysis. Among the laboratory methods, the resonant column test is one of the methods which determines the dynamic properties of soils at small strains. In this research, Young’s modulus and damping ratio of cored and reconstituted earth materials have been studied by performing resonant column test in flexural mode. The effects of consolidation stress and anisotropic consolidated stress was studied by using the Young’s modulus and damping ratio versus shear strain diagrams. The results of the study indicate that reconstituting reduces the Young’s modulus, but the variation of damping ratio versus shear strain for cored and reconstituted samples is negligible. Increase in the consolidation stress and anisotropic consolidated stress, result in the increase of Young’s modulus. Comparing the damping ratio results with the two methods of free vibration decay and half power bandwidth, indicates that the damping ratio values obtained from the half power bandwidth method are higher.