SITE PREPARATION/GAUGE POSITIONING
Preparation of the test site surface is critical to gauge performance.
This section provides site preparation procedures for both soils and
base courses and asphalt surfaces. To ensure the most accurate
gauge readings, the appropriate preparation procedure should be
followed.
SOIL AND BASE COURSE PREPARATION
Since soil surface conditions are critical to accurate
measurements, locate a level site free from any large holes,
cracks, or debris.
Smooth the surface by moving the scraper plate in a back and
forth motion. Filler such as fine sand may be used to decrease
the surface voids.
NOTE
Use only enough filler to fill the voids. Too much filler
will cause an error in the measurement.
For direct transmission measurements, put the drill rod through
the extraction tool and then through one of the guides on the
plate (see Figure 2–2).
Wearing a radiation badge and safety glasses (or other
locally approved safety devices), step on the plate and hammer
the drill rod at least 50 millimeters (2 in) deeper than the desired
test depth. The drill rod increments include the additional depth.
Remove the drill rod by pulling straight up and twisting the
extraction tool. Do not loosen the drill rod by tapping from
side to side with a hammer. This will distort the hole or cause
loose material to fall into the hole.
To ensure accurate placement of the gauge, before removing the
scraper plate mark the test area using the drill rod as shown in
Figure 2–3.
Carefully pick up the scraper plate and place the gauge on the
surface prepared by the plate. Insert the source rod into the hole
made by the drill rod. Use care when inserting the source rod,
trying not to disturb the soil around the hole.
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