2 Does
salinity affect readings?
1 Can
I use the One-Step Method if the soil varies significantly
in the compacted layer?
§ Yes.
In situations
where soils being tested are relatively
uniform, the One-Step Method is quick and easy to use.
However, where the soils vary significantly
from those used in establishing the calibration factors,
a simple field calibration adjustment
can improve test accuracy. The calibration adjustment
involves taking a sample of the soil
with a water content similar to that associated with
insitu conditions, compacting it into
a compaction mold with standard compaction energy (ASTM
D 698), making a measurement of the
weight to obtain the total density of the soil in the
mold, and then taking readings of
the soil in the mold with the TDR to obtain values of
Ka, and ECb. Research is continuing to establish the
accuracy and reliability of the adjusted calibration
factors by these procedures. (Excerpted from: Drnevich,
V.P., "New Uses of TDR, Drnevich, GeoFrontiers
Conf., ASCE,
June 30,2004, 16 pages.)
2 Does
salinity affect readings?
§ Salinity
does not affect the dielectric constant (Ka) of the soil but will affect its electric conductivity (ECb). The Two-Step Method can be
used successfuly because it does not rely on the electric conductivity of the soil. The One-Step Method cannot be used because
the calibration is done with ordinary tap water and the electric conductivity varies with salinity.
3 Does
it work in micaceous soils or caleche?
§ Yes.
The M+DI is not affected by bound water or hydrogen-bearing
materials such as micaceous soils or caleche.
4 How
deep does it work? Can you change probe lenghts?
