Percolation Test - Soil Properties: Testing, Measurement, and Evaluation - page 248

When the Martin Perk-Tester is used, data collected during this test
consist of the following:

DATA

Initial reading on the rule, r 1 (in.)
Final reading on the rule, r 2 (in.)
Elapsed time, T (min or h)

(Normally, the difference between r 1 and r 2 is 6 in.; hence, T repre-
sents the time taken for water to fall 6 in.)
If the Public Health Service procedure is followed, data collected
are the drop in water level (normally in inches) and the associated time
interval.

CALCULATIONS As mentioned, the percolation rate P is normally reported in either

inches per hour or minutes per inch. When the Martin Perk-Tester is
used, the rate in inches per hour can be calculated by dividing the
difference between r 1 and r 2 (normally 6 in.) by the elapsed time T
expressed in hours. In equation form,

r 2 r 1

P (17-1)

T

The rate in minutes per inch can be calculated by dividing T by ( r 2 r 1 ),
with T expressed in minutes.
If the Public Health Service procedure is followed, the computa-
tion is the same except that the term ( r 2 r 1 ) is replaced by the drop
in water level.

NUMERICAL
EXAMPLE

A percolation test was conducted according to the procedure described
for use with a Martin Perk-Tester. The following data were obtained:

Initial reading on rule, r 1 18.00 in.
Final reading on rule, r 2 24.00 in.
Elapsed time, T 1 h 24 min

Using Eq. (17-1), we obtain

r 2 r 1

P (17-1)

T

24.00 18.00

P 4.29 in. h

1.4

or

84

P 14.0 min in.

18.00

24.00