Measurement and Estimation of State Variables - Unsaturated Soil Mechanics in Engineering Practice - page 152

Figure 4.68 Schematic diagram of double-buffered constant-temperature bath (from Krahn and
Fredlund, 1972).

in a constant-temperature bath, as shown in Fig. 4.68. The
temperature of the bath should be maintained at a con-
stant temperature with variations on the order of

till and compacted Regina clay, respectively. The total
suction measurements were conducted using thermocouple
psychrometers. It should be noted that these relationships do
not constitute a SWCC for the soils since the results were
obtained from various soil specimens compacted at different
water contents. A SWCC describes the water content versus
suction relationship for a single soil specimen where the
applied soil suction is changed on one sample. Figures 4.70
and 4.71 indicate a rather unique relationship between soil
suction and initial water content for a particular compacted
soil, regardless of its dry densities. The in situ total suction

0.001 ◦ C
(Krahn and Fredlund, 1972). As a result, the thermoregula-
tor must be able to respond to a fluctuation in temperature
of

±

0.001 ◦ C. The soil temperature is expected to be main-
tained within the same degree of accuracy of the water bath
(or greater) due to the buffering effect of the glass beaker.
Figures 4.70 and 4.71 present measured data between
total suction and initial water content for compacted glacial

±

Figure 4.69 Stainless steel sample chamber with sealed psy-
chrometer in place (after Brown and Colllins, 1980).

Figure 4.70 Total suction versus as-compacted water content for
glacial till specimens (from Krahn and Fredlund, 1972)