Stress Effect on Creep Rates of a Frozen Clay Soil

Synopsis Differential creep tests have been carried out on frozen cylindrical clay soil samples to examine the influence of stress on creep rates. Concurrently, information was obtained concerning temperature and structure effects on the stress/creep rate relationship. Approximate linearity between logarithm of axial creep rate and axial stress (σ), for stresses greater than two-thirds the ultimate compressive strength and constant temperature, support an exponential law (exp Bσ) for predicting the effect of stress on creep rates. The hyperbolic sine law (sinh Bσ) closely approximates the exponential law for the high stresses used. The data and analysis indicate that thermal activation is involved in the creep of this frozen clay soil and that temperature (T) should appear through an expression of the form exp (–ΔF/RT). An observed activation energy (ΔF) close to 93·6 kcal/mole appears to remain constant over a range of axial stresses (600–800 lb/sq. in.) and temperatures (– 12°C to – 18°C). This constant...