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Deformation, time-dependent failure, and acoustic emissions during unconfined compression tests of frozen Fairbanks silt were studied. Acoustic emissions (AE) are detected when the applied stress exceeds a threshold level. This threshold stress is related to the limit of long-term strength of the frozen soil. Under stress exceeding the limit of the long-term strength, the accumulation of acoustic emissions with time can be correlated with creep deformation; that is, plots of the cumulative number of acoustic pulses versus time have shapes similar to those of creep curves with primary, secondary, and tertiary stages. Such correspondence made it possible to describe both phenomena from the viewpoint of the unified kinetic theory of strength. Experimental data are presented, and unified constitutive equations describing deformations, time-dependent failure, and the accumulation of the acoustic emissions during short-term creep of frozen soils are derived. The time to incipient failure, when the AE rate reaches a minimum, is considered to be the most important characteristic of a creep process. It is shown that this time can be predicted theoretically if the parameters of the AE process and the stress state of the frozen soil are known.
acoustic emission, deformation, failure silt, frozen soils, creep, rate process theory
Research civil engineer, Massachusetts Institute of Technology, Cambridge, Mass.
Research civil engineer, U.S. Army Cold Regions Research and Engineering Laboratory, Hanover, N.H.