TM 5-852-4/AFM 88-19, Chap. 4
c. A water level indicator device utilizing an
under the severe condition, encountered on construction
projects, moisture cells may not always perform
electrical contact and visual or audible signal is
37
reliably .
recommended for measuring the water table position in
d. In areas of seasonal frost, electrical
the well and may be obtained from soils testing
resistance gages and various types of pore pressure
equipment suppliers. For very shallow depths a tape or
measuring equipment (piezometers) can also be
ruler may suffice. To prevent freezing, kerosene has
employed, provided that the sensing element is located
been added in wells to displace a portion of the water
below the maximum depth of frost penetration. Freezing
column. Air pressure has also been used with limited
of water in the tubing of standpipe type piezometers can
success in sealed wells to force the water below the frost
129
and
be a problem. Carlson, Kane and Bowers
line. Since the pressure is released when a reading is
192
have reported on use of
Slaughter and Kane
taken, this method is useful only in highly permeable
piezometers in recent groundwater studies in central
soils where stability is rapidly achieved. After the
65
measurement is made, the well is again pressurized .
Alaska. Dye solutions can be used to trace the paths
209
Williams and vanEvardingar have reviewed the state-
and quantity of groundwater flows. This technique was
of-the-art of groundwater measurement in permafrost
successfully used to study ground flow in the annual
105
thaw zone at Thule AB .
regions, including use of soil moisture cells. However,
U. S. Army Corps of Engineers
Figure 7-1b. Permafrost and frost probing techniques. (Probing through frozen ground.)
7-5
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