Dynamic Tests And Constitutive Relations Of Frozen Soil

Frozen soil is widely spread in China. The22%regions of China are covered by perennial frozen soil. Studying the mechanic behavior of frozen soil is of great importance. Most current study is focused on the static or quasi-static behavior of frozen soil. Except for static and quasi-static loading, frozen soil is often subjected to dynamic loading. However, the research of frozen soil under dynamic loading is in adequate. Moreover, there is no reasonable dynamic constitutive model for frozen soil.In this research, split Hopkinson pressure bar was used to conduct impact tests for frozen soil of-3℃,-8℃,-13℃,-17℃,-23℃and-28℃. One part of these tests were conducted with negative confinement under strain rate from900to1500s-1. The other were uni-axial tests, under the strain rate range from300to1200s-1The frozen soil, showed elastic plastic behavior, was under quasi uni-axial strain condition when under negative confined test. The stress-strain curve was elastic ideal plastic under low strain rate loading, while behaved in strain hardening way under high strain rate loading. The stress-strain curve of frozen soil under uni-axial dynamic loading behaved with strain softening, showing brittle behavior. The curve ascended rapidly at the beginning until the peak, then decrease slowly.Frozen soil shows strain rate sensitivity. The peak stress and final strain of frozen soil increase with the increase of loading strain rate. Frozen soil shows temperature sensitivity. The peak stress of frozen soil increases with the lower temperature.The frozen soil specimen did not fracture after negative confined dynamic loading. Its volume decreased a little. Specimens did not broken only under the uni-axial loading with strain rate about350s-1, and totally fractured under higher strain rates. The specimen broken into more pieces under higher strain rate.In this paper, visco-elastic model with damage of frozen soil and modified Johnson-Cook model were carried out.The visco-elastic model with damage and modified Johnson-Cook model reflect the rate and temperature sensitivity and strain softening of frozen soil well.