Methods of Determining Creep, Long-Term Strength and Compressibility Characteristics of Frozen Soils

Frozen soils consisting of ice and unfrozen water possess clearly defined rheological properties. The evaluation of strength involves determining the load at which, over a given period of time, a state of equilibrium exists, which, if exceeded, causes failure. When evaluating frozen soils for deformation the load calculated is that at which the deformation reached is the maximum permissible for the structure. Equations are developed that give deformation patterns for frozen soil. Frozen soil testing for deformation may be conducted with both disturbed and undisturbed samples but the soil temperatures must be kept constant. The main features of creep curves are obtained from compression tests in the laboratory on a series of similar samples. Results are plotted of time versus deformation. At large loads an S-shaped curve is obtained showing a large deformation with complete failure occurring in a short time. For intermediate loads there is again the instantaneous deformation, followed by a very small deformation with time but at the end deformation accelerates and failure ensues. For smaller loads the instantaneous deformation occurs but this is followed by a very long period of very small or no deformation. The nature of the curves for any moment of time depends on soil type but the general pattern always remains the same. Usually an exponential relationship is assumed.SOMMAIRE FRANCAIS A SUIVREPeer reviewed: NoNRC publication: Ye