Determining the Shrinkage Limit of Soil - Soil Properties: Testing, Measurement, and Evaluation - page 107

(3) Place the shrinkage dish in the shallow pan in order to catch
any mercury overflow. Fill the shrinkage dish to overflowing with
mercury. Caution —Mercury is a hazardous substance which can
cause serious health effects from prolonged inhalation of the vapor
or contact with the skin. Remove the excess mercury by pressing
the glass plate firmly over the top of the shrinkage dish. Observe
that there is no air trapped between the plate and mercury and, if
there is, refill the dish and repeat the process. Determine the vol-
ume of mercury held in the shrinkage dish either by means of the
glass graduate or by dividing the measured mass of mercury by
the mass density of mercury (equal to 13.55 Mg/m 3 ). Record this
volume in cubic centimeters (cubic feet) of the wet soil pat, V .
Note 1 -It is not necessary to measure the volume of the
shrinkage dish (wet soil pat) during each test. The value of a
previous measurement may be used provided that it was ob-
tained as specified in (3) and the shrinkage dish is properly
identified and in good physical condition.
(4) Place an amount of the wetted soil equal to about one-third the
volume of the dish in the center of the dish, and cause the soil to
flow to the edges by tapping the dish on a firm surface cushioned
by several layers of blotting paper or similar material. Add an
amount of soil approximately equal to the first portion, and tap the
dish until the soil is thoroughly compacted and all included air has
been brought to the surface. Add more soil and continue the tapping
until the dish is completely filled and excess soil stands out above
its edge. Strike off the excess soil with a straightedge, and wipe off
all soil adhering to the outside of the dish. Immediately after it is
filled and struck off, determine and record the mass in grams
(pounds/mass) of the dish and wet soil, M w .
(5) Allow the soil pat to dry in air until the color of the soil turns from
dark to light. Oven-dry the soil pat to constant mass at 110 ± 5°C
(230 ± 9°F). If the soil pat is cracked or has broken in pieces, return
to (1) and prepare another soil pat using a lower water content. De-
termine and record the mass in g (lbm) of the dish and dry soil, M D .
(6) Determine the volume of the dry soil pat by removing the pat
from the shrinkage dish and immersing it in the glass cup full of
mercury in the following manner.
(6.1) Place the glass cup in the shallow pan in order to catch any
mercury overflow. Fill the glass cup to overflowing with mercury.
Remove the excess mercury by pressing the glass plate with the
three prongs (Figure 9-2) firmly over the top of the cup. Observe
that there is no air trapped between the plate and mercury and, if
there is, refill the dish and repeat the process. Carefully wipe off
any mercury that may be adhering to the outside of the cup.
(6.2) Place the evaporating dish in the shallow pan in order to
catch any mercury overflow. Place the cup filled with mercury in the