DEPENDENCY OF OBSERVATION PARAMETERS ON SOIL DYNAMIC PARAMETERS IN UNCONFINED IMPACT COMPRESSION TESTS

Unconfined impact compression tests were used to measure dynamic parameters of soil samples in the domains of stress wave propagation and dynamic deformation. The high-frequency equivalent Young's modulus, which was determined by the reflection theory of one-dimensional elastic stress waves, increased exponentially with water content. The low-frequency equivalent Young's modulus, which was defined as the initial gradient of a stress-strain curve, decreased exponentially with increasing water content. The high-frequency equivalent Young's modulus was one to two orders of magnitude larger than the low-frequency one. Water content, height of soil samples and drop height affected the dynamic stress-strain relationships of the soil samples. The Maxwell's viscoelastic fluid model described the stress-strain relationships well, and the values of the model parameters varied with water content and frequency.