Geohydrologic data from test hole USW UZ-6s, Yucca Mountain, Nye County, Nevada Page: 23 of 31
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Table 5. Summary of relation of gravimetric water-content measurements of composite core from
test hole USW UZ-6s to lithology and degree of welding
[Michael Chornack, U.S. Geological Survey, written commun., 1985; all data values in gram per gram]
Number StandarSd Degree of
Geologic formation of data Data range Average Median n wd
points
Tiva Canyon Member 17 0.014 to 0.040 0.027 0.030 0.008 Dense
(upper unit) of the
Paintbrush Tuff
Tiva Canyon Member 4 0.040 to 0.068 0.054 0.054 0.012 Moderate to
(lower vitrophyre) of the dense
Paintbrush Tuff
Tva Canyon Member 9 0.098 to 0.160 0.123 0.120 0.020 Partial to non-
(shardy base) of the welded
Paintbrush Tuff
Unnamed bedded tuffs 12 0.050 to 0.205 0.106 0.106 0.044 Not applicable
Topopah Spring Member 6 0.032 to 0.209 0.085 0.070 0.064 Partial
(vitric unit) of the
Paintbrush Tuff
Topopah Spring Member 17 0.010 to 0.040 0.027 0.031 0.009 Dense to
(caprock) of the moderate
Paintbrush TuffThermocouple-voltage outputs are measured
first on the calibration standards from lowest to highest
molality, followed by the rock samples; then the mea-
surements are repeated on the calibration standards
from lowest to highest molality. The before-and-after
selected voltage-output plateaus for each calibration
standard are averaged to compensate for any drift in
temperature (Brown, 1970). Each voltage-output
plateau has two temperature readings, one taken before
and one taken after the 10-minute period of voltage-
output measurements. The four temperature readings
for each calibration standard are averaged. Each rock
sample has a selected voltage-output plateau. The sam-
ple cups that contained the cuttings or core are care-
fully cleaned and dried after each set of measurements.
After all voltage-output readings are collected
and voltage-output plateaus determined for calibration
standards and rock samples, water potential is then cal-
culated for each calibration standard. The calculated
water potential is based on the molality of the calibra-
tion standard and the average temperature from the
voltage-output measurement for that calibration stand-
ard. A linear-regression equation is run based on these
calculated water potentials and the average of the
before-and-after voltage-output plateaus for each cali-
bration standard. The results of the linear-regressionequation are used to construct the calibration curve and
included intercept, slope, and coefficient of determina-
tion (r2). Using this calibration curve, the voltage-
output plateau reading from each cutting or core sam-
ple is entered into the linear-regression equation, and
the output value is the water-potential value of the sam-
ple.
Generally, measurements of water potential of
rock samples were rerun if the r2 was less than 0.990 or
if the readings did not plateau sufficiently. The calibra-
tion curves for cuttings and core from UZ-6s were
almost linear, and r2 values ranged from 0.995 to 1.000,
with most r2 values equal to 1.000.
Results of water-potential measurements for
UZ-6s are listed in tables 3 and 4 and shown in figure 5.
For depths 120.7 to 150.6 m, the water potential for
coarse cuttings averaged -37,000 kPa and that for com-
posite core averaged -2,300 kPa.
Water-potential measurements are related to the
degree of welding of tuff. Water-potential data of com-
posite core from UZ-6s, as related to geological forma-
tion and degree of welding, are summarized in table 6.
Only core data are tabulated; they are most representa-
tive of the rock units drilled.
SAMPLE TESTING PROCEDURES AND RESULTS 19
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Loskot, C.L. Geohydrologic data from test hole USW UZ-6s, Yucca Mountain, Nye County, Nevada, report, December 31, 1993; Denver, Colorado. (https://digital.library.unt.edu/ark:/67531/metadc621573/m1/23/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.