Geosynthetics August/September 2020 - 30

PVC sheet piling for cutoff and containment barriers

site in Michigan; and containment of
groundwater and soil contamination in
Corpus Christi, Texas. Key factors that
engineers used in the decision-making
process of specifying PVC sheet piles for
these projects will also be highlighted.
2a
6,507 ft-lb/ft

28.94 kN-m/m

Chemistry and permeation

Chemical compatibility tables are usually built from exposing the PVC to the
4
4
"neat" or a highly concentrated form of
122 in /ft
16,660 cm /m
the chemical approaching 100% purity.
2
2
15,000 in-lbs/in
2,625 N-mm/mm
Indeed, at extremely high concentra0.385 in
9.8 mm
tions of toluene, for example, there can be
deleterious effects on PVC ranging from
2b
254 mm
10.0 in
degradation to swelling to softening. At
8,480
37.71
kN-m/m
762 mm
30 inft-lb/ft
lower concentrations, the degradation
3
3
31.8
in /ft
1,710 cm /m
does not occur (Berens 1985).
Weatherable
Rigid Vinyl
4
4
In Berens' investigation, "Prediction
159
in /ft
21,700 cm /m
Grey,
Clay
of
Organic Chemical Permeation
2
2
15,000
in-lbs/in
2,625 N-mm/mm
Box Profile,
I-Beam Lock, XCR
through PVC Pipe," he concludes,
"Softening and significant permeation
2c
0.480
in
12.2 mm
6 sheets/bundle
of PVC pipe seems possible only in the
10.0 in
254 mm
presence of nearly undiluted solvents or
FIGURE 2a, 2b, and 2c PVC sheet pile
18 in
457 mm
swelling agents for PVC. At lower activi5,467 lb-ft/ft
24.32 kN-m/m
shapes: (2a) Box profile; (2b) Z-profile;
ties [concentrations], which still corre(2c)
Flat
panel
Weatherable
Rigid Vinyl
.385"
3
3
1,102 cm /m
20.5 in /ft
spond to unusually high levels of enviGrey, 4Clay
4
ronmental pollution, solvent transport
45 in /ft
6,145 cm /m
follows ideal Fickian diffusion kinetics.
Z Profile, I-Beam Lock, XCR
2
2
13,750 in-lbs/in
2,406 N-mm/mm . . . The calculated permeation rates are
12 sheets/bundle
virtually zero for many centuries, indi0.250 in, 30
0.240
in
6.4 mm, 6.1 mm
"
cating that rigid PVC pipe is an effective
barrier against permeation of environ7.0 in
178 mm
mental pollutants" (1985).
24 in
610 mm
Mao et al. (2011) validated and
ademarks and patents owned by CMI Limited Co.
.480
"
built on Berens' research and develWeatherable
Rigid
Vinyl
oped a predictive model based on the
Textured Grey, Textured Clay
behavior of toluene (the more aggressive PVC solvent component of BTEX)
Flat Profile, I-Beam Lock
in National Institute of Standards and
18"
8 sheets/bundle
Technology (NIST) fuel. Equation 1 from
g., an anchored wall) where legs are fully and continuously soil supported and the flat face is in bending
"Microscopic Visualization Technique
hose with more complex configurations will most likely require a reduction in the sheet pile's design capacity.
to Predict the Permeation of Organic
demarks and patents owned by CMI Limited Co.
Solvents through PVC Pipes in Water
24"
Distribution Systems" relates the swollen layer to the chemical's concentration
.250"
and time.
3

3

24.4 in /ft

1,312 cm /m

TM

TM

Applying this equation (Equation 1)
(1)
where:
Ls = swollen layer thickness (mm)
vf = volume fraction concentration
t = time (days)
to three common PVC sheet pile products
results in the predictions for permeation
shown in Figures 2a, 2b and 2c. At lower
concentrations, the time to permeate a
given thickness is on the order of centuries.
Additionally, in the Practical Handbook
of Environmental Site Characterization
and Ground-Water Monitoring (Nielsen
2005), Ranney and Parker concluded from
their research with known PVC solvents
(see List of known PVC solvents), many
of which are on the U.S. Environmental
Protection Agency's (EPA) volatile
organic compound (VOC) and semi-volatile organic compound (SVOC) target
list, that at concentrations of 10% or less,
there was no measurable degradation of
PVC sample well casings:
List of known PVC solvents
Nielsen 2005)
Hydrocarbons (aliphatic
and aromatic)
*	 Benzene
*	 Gasoline (93 octane, unleaded)
*	 Hexane (85% N-hexane)
*	 Kerosene (K-1)
*	 Toluene
*	 o-Xylene
Chlorinated solvents (aliphatic
and aromatic)
*	 Bromochloromethane
*	 Carbon tetrachloride
*	 Chlorobenzene
*	 Chloroform
*	 1,2-Dichlorobenzene
*	 1,2-Dichloroethane
*	 trans-1,2-Dichloroethylene
*	 Methylene chloride

"

30

.250"

Geosynthetics | August September 2020

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Geosynthetics August/September 2020

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