13. ABSTRACT (cont'd)
moist the silty soil is. Under the conditions of this study, maximum frost penetration is 61 cm ("cold-
est" surface boundary condition, 25% moisture content soil, no sand inclusion). The change in maxi-
mum frost depth because of the presence of a wide sand inclusion is large relative to overall frost pene-
tration. Similarly, the difference in soil temperature at a given depth, although small, can correspond
to a large difference in unfrozen moisture content of the silty soil. Under either relatively mild or "nor-
mal New England" winter conditions, the presence of a sand inclusion is probably beneficial to the
performance of a buried electromagnetic sensor system, which is more reliable in dry or frozen soil be-
cause of the soil's lower electrical conductivity. A sand inclusion may not lead to improved sensor per-
formance under more severe winter conditions, which cause much lower soil temperatures and much
deeper frost penetration.
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