Partial saturation leads to a significant decrease in the short- and long-term strength of frozen sands and gravels so that the stability of the frost body can be impaired in artificial ground freezing applications. Uniaxial and triaxial compression tests with on-unit cooling were performed on sand to determine uniaxial compressive strength, creep resistance and shear parameters. The results confirm and complete the findings from the few previous studies. Investigations on undisturbed specimens of medium and high plasticity clay using the same testing technique illustrate the influence of the consistency limits and the increase in short- and long-term strength at lower temperatures.