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th
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greater differences than the ones actually present in the
soil.
Based on the foregoing, one must try to ensure that the value of
the coefficient of permeability is determined at least to ± 20-
30% accuracy.
6 REFERENCES
Casagrande A. 1938. Seepage through dams, J.N. Engl. Water Works
Association, L1(2), pp 131 -172.
When evaluating measured values, one must bear in mind that
no measurement is perfect and each method of measurement
carries an error, hence each will distort measured values one
way or another. Drilling (or pressing the probe into position)
may destroy the structure of the soil in in-situ measurements.
When drilling in floating sand or sand meal, fresh water should
always be replenished and the bit has to be withdrawn slowly
enough to prevent the soil from breaking into the borehole due
to the emanating piston effect. When performing laboratory
measurements of an undisturbed sample, taking samples with a
chipped sampler vessel is a dangerous source of errors as we
will measure the volume of water flowing past the mantle.
When evaluating measured values, one must pay attention to the
direction of change in the measured value triggered by the
measurement error. A chipped sampler will lead to measuring a
larger value of permeability, while the soil compacted by the
probe will reduce the measured value.
Darcy H. 1856.
Les fontaines publiques de la ville de Dijon
. Dalmont,
Paris.
Galli L. 1968. Planning of dikes, (in Hungarian), VIZITERV tervezési
segédletek, 11. kötet, Vízügyi Tervező Vállalat.
Hazen A. 1895. The filtration of public water-supplies, New York.
Kézdi, Á. 1976. Soil mechanics, (in Hungarian), Tankönyvkiadó,
Budapest
Kovács Gy. 1972. Seepage hydraulics, (in Hungarian), Akadémiai
Kiadó, Budapest
Lumb P. 1966. The variability of natural soils. Canadian Geotechnical
Journal Nr 3.
Mlynarek, Z. 2010. Quality of in situ and laboratory tests contribution to
risk management.
Nagy L. 200. Geotechnical questions of flood dikes, (in Hungarian).
Vízügyi Közlemények, (2000), LXXXII. évf., Vol. 1., pp. 121-146.
Nagy L. 2007. Flood defence against dike slope slide, (in Hungarian).
Innova-Print Kft. nyomda, ISBN 978-963-87073-9-0.
Nagy L. 2008. A comparative study of the permeability (in Hungarian),
Kézdi memorial conference, (2008), pp. 97-106, Budapest, ISBN
978-963-06-5725-9.
We cannot say what the coefficient of permeability of the soil
is, we can only state the value we received by performing a
certain type of measurement. And even if we do that, we need to
take into account the disturbance of the soil sample, the errors
of our method, etc. One must examine the method used to
produce the result as well as the distribution of the result and the
error lodged in the examination.
Rózsa L. (editor) 1977. Foundation engineering handbook (in
Hungarian), Műszaki kiadó.
Uzielli M. 2008 Statistical analysis of geotechnical data. Proceedings of
Geotechnical and Geophysical Site Characterization Conference,
Balkema, Taiwan, Taylor, Frances 2008.
Presenting the above measured values helps us orientate
ourselves among the mysteries of the coefficient of
permeability. The poorest conclusion one can draw is that the
value of the coefficient of permeability is uncertain and
therefore there is no need to determine it. One should not follow
that road: on the contrary, one should underpin soil mechanics
opinions by sound measurements.
1,00E-08
1,0E-08
1,0E-07
1,0E-06
1,0E-05
1,0E-04
1,0E-03
1,0E-02
1,0E-01
1,0E+00
1,0E+01
1,0E+02
Measure in triaxial cell
Menard-probe
Zamarin-equatation
Khafagi-probe
Constanthead test
Beyer-table
Foundationhandbook
Fallinghead test
cm/s
Oedometermeasures
Watertight limit
(Kézdi 1976)
Grain sizedistributioncurves
Wellwatertight
Poorlywatertight
Poorlypermeable
Wellpermeable
Excellentpermeable
Notdewaterable
Watertight coreofdams
Filteranddrain zonesofdams
Poorlydewaterable
Welldewaterable
Watertight limit
(MSZ 15221)
Figure 3. Soil permeability characteristics and the ranges of
determining the coefficient of permeability
