Abstract:
The effects. of moisture, cation concentration, dens ity ,
temper~ t ure and grai n si ze on the electrical resistivity
of so il s are examined using laboratory prepared soils. An
i nexpen si ve method for preparing soils of different
compositions was developed by mixing various size
fractions i n the laboratory. Moisture and cation
c oncentration are related to soil resistivity by powe r
functions, whereas soil resistiv ity and temperature,
density, Yo gravel, sand , sil t, and clay are related by
exponential functions .
A total of 1066 cases (8528 data) from all the
experiments were used in a step-wise multiple linear
r egression to determine the effect of each variable on
soil resistivity. Six variables out of the eight variables
studied account for 92.57/. of the total variance in so il
resistivity with a correlation coefficient of 0.96. The
other two variables (silt and gravel) did not increase the
· variance. Moisture content was found to be - the most
important
Yo clay.
variable- affecting s oil res istivi ty followed by
These two variables account for 90.81Yo of the
total variance in soil resistivity with a correlation
~oefficient ·.of 0 . 95. Based on these results an equation to
' ~~ed{ ct soil r esist ivi ty using moisture and Yo clay is
developed .
To t est the predicted equation, resistivity measurements were made on natural soils both in s i tu a nd
i n the laboratory. The data show that field and laboratory
measurements are comparable. The predicted regression line
c losely coinciqes with resistivity data from area A and
area B soils ~clayey and silty~clayey sands). Resistivity
data and the predicted regression line in the case of
c layey soils (clays> 40%) do not coincide, especially a t
l ess than 15% moisture. The regression equation
overestimates the resistivity of so i l s from area C and
underestimates for area D soils. Laboratory prepared high
clay soils give similar trends. The deviations are
probably caused by heterogeneous distribution of mo i sture
and difference in the type o f cl ays present in these soils.
