Calculated stiffness values, based on measured deflections under loading of a pavement surface, for a thin pavement structure are given in Fig. 8.6, along with the water content. One can see that the spring-thaw period started in early April as the water content at the three probes increased from 4%-7% to 12%-16% in a very short period of time. When the water content in the lower part of the granular base reached its maximum value (15.2%), the stiffness of that layer reached its minimum value. As the water content during the summer period gradually decreased to 11%, the stiffness increased to its maximum value. The same trend was mainly true for the subgrade as well. The water content of the subgrade though reached its lowest value much later than the granular base and the recovery went on during the whole summer. This is probably due to the subsoil having much higher fines content than the base and the sub-base and, therefore, it takes much longer time for the water to dissipate from the subgrade.
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Increased use of dielectric sensors (see Chapter 3, Section 3.2.2) have permitted moisture assessments to be continued during cold-climate winters. By this means it has been observed that complete freezing of all pore moisture doesn’t necessarily occur in all the granular pavement layers, even though they are, nominally, within the frost-affected depth.
