Axial compression stress path tests on artificial frozen soil samples in a triaxial device at temperatures just below 0 °C

This paper aims to assess the characteristics of the strength and creep properties of frozen soil under triaxial stress conditions at temperatures close to the thawing point. A series of triaxial constant rate of strain (CRS) and constant stress creep (CSC) tests was carried out in axial compression on artificially frozen soil samples at temperatures between -3.0 and -0.3 degrees C. Acoustic emissions, with a frequency range of 100-1000 kHz, were measured using a wide-band piezoelectric sensor to understand the mechanisms of the deformation behaviour and microstructural effects that control the response of the frozen soil specimens during the tests, especially at yield and approaching failure. The test results showed that the influence of a temperature increase close to the thawing point led to reduced shear strength and increased minimum axial strain rate. The test results were compared with data from similar experiments on artificial frozen and alpine permafrost specimens obtained from a past research project. It was observed that the acoustic emission response indicates a change in the physical process of deformation between microcrack formation and the reorientation of ice granules, depending on the strain rate.