36
Geotechnical News •September 2015
GEOSYNTHETICS
Although both gradient ratio test
devices yielded a similar response, the
ability to test at high effective stress
assured saturation of the specimen in
the flexible-wall device, which was
believed to reduce the time required to
complete the test.
Williams and Abouzakhm (1989) had
earlier used a modified triaxial perme-
ability device to develop the general
concept of the Hydraulic Conductivity
Ratio (HCR) test in a flexible-wall
permeameter. The value of conductiv-
ity ratio is now defined by:
HCR = k
sg
/k
sgo
where:
k
sg
= hydraulic conductivity of the
soil-geotextile system at any time
during the test
k
sgo
= initial hydraulic conductivity of
the soil-geotextile system at the
beginning of the test
The test device allows for back-
pressure saturation and consolidation
of the test specimen, prior to imposing
seepage. In common with the gradi-
ent ratio test device, the geotextile is
placed at the base of the soil specimen.
Downward seepage flow establishes
a value of k
sgo
, and k
sg
is then mea-
sured over a time period sufficient
for approximately 5 pore volume
exchanges. The methodology has been
standardized as a performance test,
and is intended for soil with a hydrau-
lic conductivity less than or equal to 5
x 10
-2
cm/s (ASTM D5567).
References
ASTM D5101. Standard Test Method
for Measuring the soil-geotextile
clogging potential by Gradient
Ratio. ASTM International, USA.
ASTM D5567. Standard Test Method
for Hydraulic Conductivity Ratio
(HCR) Testing of Soil/Geotextile
Systems. ASTM International,
USA.
Austin, D.N., Mlynarek, J. and Blond,
E. (1997). Expanded anti-clogging
criteria for woven filtration geotex-
tiles. Proc. Geosynthetics ’97,
Long Beach, CA, 1997, Industrial
Fabrics Association International,
pp.1123-1144.
Bailey, T.D., Harney, M.D. and Holtz,
R.D. (2005). Rapid assessment
of geotextile clogging potential
using the flexible wall Gradient
Ratio test. Proc. Geo-Frontiers ’05,
doi:10.1061/40782(161)1.
Calhoun, C. (1972). Development
of design criteria and acceptance
specifications for plastic filter
cloths. Technical Report S-72-7
U.S. Army Corps of Engineers,
Waterways Experiment Station,
Vicksburg, USA, 98p.
Fannin, R.J., Vaid, Y.P. and Shi, Y.C.
(1994a). Observations on the Gra-
dient Ratio test. ASTM Geotech.
Testing J., 17:35-42.
Fannin, R.J., Vaid, Y.P. and Shi, Y.C.
(1994b). Filtration behaviour of
nonwoven geotextiles. Can. Geo-
tech. J., 31: 564-569.
Fannin, R.J., Vaid, Y.P., Palmeira,
E.M. and Shi, Y.C. (1996). A
modified Gradient Ratio test
device. ASTM Spec. Tech. Pub.
1281 (Eds. S.K. Bhatia and L.D.
Suits), Denver, CO, 20 June 1996,
pp.100-112.
Fannin, R.J. and Srikongsri, A. (2007).
Geotextile filters in cyclic flow:
test results and design criteria.
Proc. Geosynthetics ’07, Wasing-
ton, DC, 16-19 Jan. 2007, pp.170-
185.
Haliburton, T.A. and Wood, P.D.
(1982). Evaluation of the US Army
Corps of Engineers Gradient Ratio
test for geotextile performance.
Proc.2nd Int. Conf. on Geotextiles,
Las Vegas. USA, 1:97-102.
Hameiri A. and Fannin R.J. (2002). A
cyclic gradient ratio test device.
ASTM Geotech.Testing J., 25:266-
276.
Harney, M.D. and Holtz, R.D. (2001).
A flexible wall Gradient Ratio test.
Proc. Geosynthetics ’01, 12-14
Feb. 2001, Portland, OR, pp.409-
422.
Holtz, R.D., Christopher, B.R. and
Berg., R.R. (1997). Geosynthetics
Engineering. BiTech Press, Rich-
mond, B.C., 452p.
Lafleur, J., Francoeur, J., and Faure,Y.
(2002). Piping, bridging and
blinding of geotextiles as evalu-
ated from the Gradient Ratio test.
Proc.7th Int. Conf. on Geosynthet-
ics, Nice, France, pp.1069-1074.
Palmeira E. M., Gardoni M.G. and
Bessa da Luz D.W. (2005). Soil-
geotextile filter interaction under
high stress levels in the gradient
ratio test. Geosynthetics Interna-
tional, 12:162-175.
Schiereck, G.J. (2003). Introduction to
Bed, Bank and Shore Protection.
Taylor and Francis, 399p.
Srikongsri, A. and Fannin, R.J. (2009).
Retention capacity of geotextile
filters in cyclic flow. Proc. Geo-
synthetics ’09, Salt Lake City, UT,
24-27 Feb. 2009, pp.498-508.
USACE (1977). Specification for
Plastic Filter Fabric. Civil Works
Construction Guide no.CW02215.
US Army Corps of Engineers, 7p.
Williams, N.D. and Abouzakhm, M.A.
(1989). Evaluation of geotextile/
soil filtration characteristics using
the Hydraulic Conductivity Ratio
analysis. Geotextiles and Geo-
membranes, 8:1-26.
