Determination of soil strength during spring thaw is essential to developing mechanistically determined seasonal load restrictions. The work reported uses shallow refraction techniques to determine p-wave velocities of the road subgrade at weekly intervals. From this information, the variation of p-wave properties with time is developed. From the relationship between p-wave velocity and time, it is shown that p-wave velocity starts at relatively high values before thaw commences, decreases to a minimum, and then increases. The minimump-wave velocity occurs at about 3 weeks after the maximum degree-days for the freezing season. Results from the p-wave tests are shown to be comparable to results obtained using a clegg impact test. However, the minimum clegg value occurs at an earlier date than the minimum p-wave velocity. Overall, results indicate that shallow refraction surveys can be used to develop a curve of p-wave velocity versus time. This relationship, in turn, can be related to a soil strength value that would be usable in a mechanistic pavement design method. This paper appears in transportation research record no. 1291, Fifthinternational conference on low-volume roads, may 19-23, 1991, raleigh, north carolina, volume 2
Samenvatting