Permeability Test for Granular Soils (Constant-Head Method) - Soil Properties: Testing, Measurement, and Evaluation - page 254

situation being investigated, samples of the finer, average, and
coarser soils should be obtained for testing.

(3) From the material from which the oversize has been removed
[see (2) above], select by the method of quartering a sample for
testing equal to an amount approximately twice that required for
filling the permeameter chamber.

(1) The size of permeameter to be used shall be as prescribed in
Table 18-1.

PREPARATION OF
SPECIMENS [1]

(2) Make the following initial measurements in centimeters or
square centimeters and record on the data sheet: the inside diameter,
D , of the permeameter; the length, L , between manometer outlets;
the depth, H 1 , measured at four symmetrically spaced points from
the upper surface of the top plate of the permeability cylinder to the
top of the upper porous stone or screen temporarily placed on the
lower porous plate or screen. This automatically deducts the thick-
ness of the upper porous plate or screen from the height measure-
ments used to determine the volume of soil placed in the
permeability cylinder. Use a duplicate top plate containing four
large symmetrically spaced openings through which the necessary
measurements can be made to determine the average value for H 1 .
Calculate the cross-sectional area, A , of the specimen.

(3) Take a small portion of the sample selected as prescribed in (3)
in the section “Sample” for water content determinations. Record
the weight of the remaining air-dried sample, W 1 , for unit weight
determinations.

(4) Place the prepared soil by one of the following procedures in uni-
form thin layers approximately equal in thickness after compaction
to the maximum size of particle, but not less than approximately
15 mm (0.60 in.).

(4.1) For soils having a maximum size of 9.5 mm ( 3 ⁄ 8 in.) or less, place
the appropriate size of funnel, as prescribed in the section “Appa-
ratus and Supplies,” in the permeability device with the spout in

Table 18-1 Cylinder Diameter [1]

Minimum Cylinder Diameter

Less than 35% of
Total Soil Retained
on Sieve Opening

More than 35% of
Total Soil Retained
on Sieve Opening

Maximum
Particle Size
Lies between Sieve
Openings

2.00 mm
(No. 10)

9.5 mm
( 3 ⁄ 8 in.)

2.00 mm
(No. 10)

9.5 mm
( 3 ⁄ 8 in.)

2.00 mm (No. 10) and
9.5 mm ( 3 ⁄ 8 in.)

76 mm
(3 in.)

— 114 mm

(4.5 in.)

—

9.5 mm ( 3 ⁄ 8 in.) and
19.0 mm ( 3 ⁄ 4 in.)

— 152 mm

(6 in.)

—

229 mm
(9 in.)