Seasonal Soil Strength by Spectral Analysis of Surface Waves

Spectral analysis of surface waves (SASW) is a nondestructive test technique that can be used to determine profiles of surface‐wave velocity versus depth. In this work, the technique is used to determine the wave‐velocity profile at a selected site at several different days during the spring thaw periods of 1989 and 1990. The test technique uses standard procedures using two accelevometers connected to a spectral analyzer. Results from each test are processed using a desktop computer and programs developed specifically for analysis of the data. Over 200 tests are done on 20 different days, and results are summarized in the paper. Specific results indicate that the SASW technique has excellent potential for detecting time‐varying changes in soil properties. In particular, the results indicate that wave velocities at a given depth tend to start high (frozen soil), decrease to a low value (thawed wet soil), then increase (thawed dry soil) as the spring thaw period progresses. In addition, results show a good correlation between calculated thaw depth and thaw depth estimated from SASW techniques.