Permeability Test for Fine-Grained and Granular Soils (Falling-Head Method) - Soil Properties: Testing, Measurement, and Evaluation - page 273

with base plate and gasket attached plus compacted soil and also
measure the length of the specimen in centimeters. Determine the
dry density and void ratio of the specimen.
(3) Place a piece of porous disk on the top of the specimen and a
spring on the porous disk. Carefully clean the permeameter (mold)
rim. With its gasket in place, press down the top (cover) plate
against the spring and attach it securely to the top of the perme-
ameter cylinder, making an air-tight seal. The spring should be
compressed and should apply a pressure to the compacted soil spec-
imen to keep it in place when it is saturated with water.
(4) Place the permeameter in a sink in which the water is about
2 in. above the cover. Be sure the outlet pipe is open so that water
can back up through the specimen. This procedure will saturate the
sample with a minimum amount of entrapped air. When water in
the plastic inlet tube on top of the mold reaches equilibrium with
water in the sink (allowing for capillary rise in the tube), the spec-
imen may be assumed to be saturated. (A soaking period of 24 h
might provide better results.)
(5) With the water level stabilized in the inlet tube of the perme-
ability mold, take a hose clamp and clamp the exit tube. Remove
the permeameter from the sink and attach it to the rubber tube at
the base of the burette, which has been fastened to a ring stand
(Figure 19-1). Fill the burette with water from a supply, which
should be temperature-stabilized (and de-aired if desired).
(6) Now de-air the lines at the top of the specimen by opening the
hose clamp from the burette and opening the petcock on top of the
cover plate. Allow water to flow (but keep adding water to the bu-
rette so it does not become empty) from the petcock. When no more
air comes out, close the petcock. Do not close the inlet tube from the
burette. Remember that the exit tube is still clamped shut.
(7) Fill the burette to a convenient height, and measure the
hydraulic head across the sample to obtain h 1 (see Figure 19-1).
(8) Open the exit tube (and petcock) and simultaneously start
timing the test. Allow water to flow through the sample until the
burette is almost empty. Simultaneously record the elapsed time
and clamp only the exit tube. Measure the hydraulic head across
the sample at this time to obtain h 2 (see Figure 19-1). Take the
temperature each time.
(9) Refill the burette and repeat (8) two additional times. Take the
temperature each time.
(10) To check on whether the sample is saturated, one may collect
the water coming out of the exit tube and compare this volume with
that entering the sample. Obviously, if
q out q in
the specimen was not saturated.