-
prite
heji Unf Ed
on ouffeabil70 M
centrations. Salinity effects of inltrating solutions on
swelling pressure and hydraulic conductivity of tested sam-lts
obtained show that the swelling pressure of GMZ01 bentonite
decreases withnltrating solutions, while the degree of the impact
decreases with the increase of
ity, goontonite
waste (HLW). During the construction and long-term operation of
a cantly lower swelling pressure (~2 MPa) was obtained with low
ionic
ect of synthetic seawa-g the important role of
al composition of pore
Engineering Geology 166 (2013) 7480
Contents lists available at ScienceDirect
Engineering
j ourna l homepage: www.e lsinuence the swelling pressure of
bentonite. Karnland et al. (2006)found that the swelling pressure
ofMX-80 bentonite decreases as the sa-linity of pore water
increases. Conrmation was made by Castellanos
uid has signicant inuence on the hydraulic conductivity of
compactedbentonite. The hydraulic conductivity of Wyoming
Nabentonite in-creases with increase of concentration of the
inltrating solutiontions (Herbert et al., 2008). This can affect
the physical and chemicalproperties of bentonite, such as the
mineralogical composition andswelling capacity etc.
Previous studies show that salt content of pore uid can
signicantly
sure than de-ionized water did. Moreover, the effter was found
depending on bentonite, evidencinsoil mineralogy in this
process.
Literature reports also show that the chemicgeological
repository, compacted bentonite can work as an effectivebarrier,
protecting the canister and restricting the transfer of
radionu-clide released from the waste packages after possible
failure of canister(Wersin et al., 2007). Meanwhile, interaction
can take place betweencompacted bentonite and groundwater of
certain chemical composi-
concentration solutions and the lowest one (b1 MPa) was
recordedwith high saline brines. Based on investigation of the
inuence of syn-thetic seawater on the swelling pressure of ve
common bentonites:Kunigel-VI, Volclay, Kunibond, Neokunibond and
MX-80, Komime et al.(2009) also conrmed that synthetic seawater
gave lower swelling pres- Corresponding author at: Key Laboratory
of GeotechnicofMinistry of Education, Tongji University, Shanghai
200092fax: +86 21 6598 2384.
E-mail address: [email protected] (W.-M. Ye).
0013-7952/$ see front matter 2013 Elsevier B.V. All
rihttp://dx.doi.org/10.1016/j.enggeo.2013.09.001has been considered
asgineering barrier in deepevel radioactive nuclear
ion content on the behavior of MX-80 bentonite. Observations
showedthat the swelling pressure of MX-80 bentonite reaches the
highestvalue (N4 MPa) when it was hydrated with de-ionized water, a
signi-buffer/backll material for construction of engeological
repository for disposal of high-lSwelling pressureHydraulic
conductivityDDL
1. Introduction
Due to its low hydraulic conductivsorption properties etc.,
compacted bedraulic conductivity of GMZ01bentonite increaseswith
the increase of solution concentrations. Comparison showsthat the
impact of NaCl solutions on the swelling pressure and hydraulic
conductivity is higher than that of CaCl2solutions at same
concentrations. This may be explained by the impact of cation types
on the microstructure ofbentonite.
2013 Elsevier B.V. All rights reserved.
d swelling capacity and
et al. (2008) on the FEBEX bentonite: an increase in salt
concentrationdecreases the swelling pressure, but this decrease is
less signicant incase of high density. Herbert et al. (2008)
investigated the inuence ofSalt solutionGMZ01
bentoniteBuffer/backll materials
concentrations. Moreover, swelling pressure reaches stability
more rapidly in case of high concentrations. The hy-Keywords: ples
were investigated. Resuincreasing concentration of iInuence of salt
solutions on the swellingconductivity of compacted GMZ01 benton
Zhu Chun-Ming a, Ye Wei-Min a,b,, Chen Yong-Gui a, Ca Key
Laboratory of Geotechnical and Underground Engineering of Ministry
of Education, Tongb United Research Center for Urban Environment
and Sustainable Development, the Ministry oc Laboratoire Navier,
Ecole des Ponts ParisTech, France
a b s t r a c ta r t i c l e i n f o
Article history:Received 16 January 2013Received in revised form
30 August 2013Accepted 2 September 2013Available online 6 September
2013
During the long-termoperaticompositions can affect the bswelling
pressure and permehas an initial dry density of 1.al andUnderground
Engineering, China. Tel.:+862165983729;
ghts reserved.essure and hydraulic
n Bao a, Cui Yu-Jun a,c
iversity, Shanghai 200092ucation, Shanghai 200092
f a deep geological repository, inltration of groundwaterwith
different chemicalr/backll properties of compacted bentonite. Using
a newly developed apparatus,ity testswere carried out on densely
compactedGMZ01 bentonite samples,whichg/m3,with de-ionizedwater
aswell as NaCl and CaCl2 solutions at different con-
Geology
ev ie r .com/ locate /enggeo(Studds et al., 1998). This
observation was conrmed by Villar (2005),who found that the
hydraulic conductivity ofMX-80 bentonite inltratedwith pore water
with a salinity of 0.5% was 135% higher than that withde-ionized
water. The hydraulic conductivity of a bentonitesand mix-ture
increased 6 times, when inltration uid changed from de-ionizedwater
to 16 g/L salt solution (Mata, 2003). A possible explanation to
-
these observations is that the salinity of inltrating solutions
inuencesthe swelling of aggregates, and in turn, changes the
microstructure ofbentonite, resulting in changing of the hydraulic
conductivity (Puschet al., 1990; Suzuki et al., 2005).
The program for deep geological disposal of high-level
radioactivewaste in Chinawas launched in themiddle of 1980s. Based
on a nation-wide survey, Beishan, in Gansu province, China, has
been selected as oneof the potential disposal sites. Related eld
work including geologicaland hydrogeological investigations has
been carried out. Results showthat the total dissolved solids
(TDS), which is rich in Na+ and Ca2+,in the groundwater in
Yemaquan, Beishan area, changes from 2 g/Lto 80 g/L. The main
chemical compound is ClSO4Na, followed byClSO4NaCa (Guo et al.,
2001). This large variability in terms of chem-ical compositions of
groundwater justies the study on the inuence of
75C.-M. Zhu et al. / Engineering Geology 166 (2013)
7480inltrating liquid on the swelling pressure and hydraulic
conductivity ofcompacted GMZ01 bentonite.
In this study, the swelling pressure and hydraulic conductivity
ofcompacted GMZ01 bentonite (1.7 Mg/m3 dry density) were
investigat-ed with different inltrating solutions: de-ionized water
and solutionsof sodium chloride (NaCl) and calcium chloride (CaCl2)
at different con-centrations. The results obtained were analyzed in
terms of microstruc-ture changes.
2. Experimental investigations
2.1. Materials
The GMZ01 bentonite studied was taken from GaoMiaoZi (GMZ)in the
Inner Mongolia Autonomous Region, 300 km northwest fromBeijing,
China (Ye et al., 2009). It is a light gray powder, dominated
bymontmorillonite (75.4% in mass). As a Nabentonite, its basic
physicaland chemical properties are presented in Table 1 (Wen,
2006). A highcation exchange capacity and adsorption ability can be
identied (Yeet al., 2010, 2012).
The salts NaCl and CaCl2 used in this test were of analytical
grade,corresponding to a purity of 99%.
2.2. Test apparatus
The experimental setup for the swelling pressure and hydraulic
con-ductivity test with salt solutions is shown in Fig. 1. It is
composed of fourparts: a testing cell, a pressurevolume controller,
a fresh/saline waterconversion device and a data logger (Fig.
1(b)).
The testing cell contains a basement, a metallic sample ring,
two po-rous stones, a stainless steel piston, a top cover, a
pressure sensor andfour screws for xing all parts together (Fig.
1(a)). Two outlets aredesigned in the basement, one is connected to
the pressurevolumecontroller and the second is used for air
expulsion. A load sensor isplaced between the top cover and the
stainless steel piston for monitor-ing the swelling pressure. The
pressurevolume controller (032 MPato an accuracy of 1 kPa; 0200 cm3
to an accuracy of 1 mm3) is
Table 1Basic physical and chemical properties of GMZ01 bentonite
(Wen, 2006).
Property Description
Specic gravity of soil grain 2.66pH 8.689.86Liquid limit (%)
276Plastic limit (%) 37Total specic surface area (m2/g) 597Cation
exchange capacity (mmol/100 g) 77.3Main exchanged cation (mmol/100
g) Na+ (43.36), Ca2+ (29.14),
Mg2+ (12.33), K+ (2.51)Main minerals Montmorillonite
(75.4%),
Quartz (11.7%),Feldspar (4.3%),Cristobalite (7.3%)employed for
application of a stable injection water pressure and mea-surement
of the volume of water injected.
As salt solutions cannot be directly used in the
pressure/volumecontroller, a fresh/saline water conversion device (
in Fig. 1(b)) isdesigned. It is made of Plexiglas, one end is
connected to the pressurevolume controller and the other end is
connected to the basement. De-ionizedwater and salt solution can be
lled in the two parts respectively,which are separated by the
silicone oil kept between them.
2.3. Test procedures
2.3.1. Sample preparationAccording to the target cylindrical
sample with a height of 10 mm, a
diameter of 50 mm and a dry density of 1.70 Mg/m3 to be
compacted,GMZ01 bentonite powder at an initial water content of
10.76% wasweighted (37 g) and put into a cylindrical column.
Compaction loadwas applied through a piston at a rate of 0.4 kN/min
to a maximumvalue of 48 kN. Then, the maximum load was kept for 1
h. After that,the sample was immediately put into the testing cell
( in Fig. 1(a))with the metallic sample ring for the swelling
pressure and hydraulicconductivity test.
De-ionized water and 8 solutions at desired saline
concentrations(Table 2) were employed for the inltration tests.
2.3.2. Swelling pressure testsAfter the compacted GMZ01
bentonite sample was introduced into
the testing apparatus as shown in Fig. 1, solutions at different
concen-trationswere inltrated into the sample through thewater/salt
convert-er under a pressure of 100 kPa. Air-bubbles in the test
system wereexhausted. The temperature was maintained at 20 1 C. The
volumeof injected solution and the evolution of swelling pressure
wererecorded. When the sample was saturated (which was
characterized bythe stabilization of swelling pressure, Villar and
Lloret, 2004), the swell-ing pressure test was considered as
completed. The constant-volumemethod was employed for determination
of the swelling pressure ofcompacted samples tested.
2.3.3. Hydraulic conductivity testsThe constant hydraulic head
method was employed for the determi-
nation of saturated hydraulic conductivity. After completion of
the swell-ing pressure test mentioned above, the hydraulic
conductivity test wasconducted on the same sample. For this
purpose, the injection pressurewas increased to 1 MPa and was
maintained during the whole test.The volume of solution injected
was recorded by the volume/pressurecontroller. When the volume of
inltration solution injected reached astable state, the test was
stopped. Based on the results obtained, thehydraulic conductivity
was determined using Darcy's Law.
3. Test results and discussions
3.1. Swelling pressure
3.1.1. Impact of concentrationInuences of concentration of
inltration solutions on the swelling
pressure of compacted GMZ01 bentonite are presented in Figs. 2
and3. It can be observed that the swelling pressure decreases
from5.11 MPa (de-ionized water) to 3.06 MPa (2.0 M NaCl solution)
and3.6 MPa (2.0 M CaCl2 solution). Namely, the swelling pressure of
thecompacted GMZ01 bentonite decreases as the concentration of the
inl-tration solutions increases. This conclusion is consistentwith
the resultsreported by different researchers (Karnland et al.,
2006; Castellanoset al., 2008; Herbert et al., 2008; Komime et al.,
2009; Siddiqua et al.,2011; Lee et al., 2012).
Figs. 2 and 3 also present that the evolution curves of
swellingpressure of samples inltrated with low concentration
solutions are
double-peak shaped. Namely, the swelling pressure increases at
the
-
matic diagram ensor 5Top cover 6Ring 7Basement 8
12Pressure/volume controller 13Data logger
76 C.-M. Zhu et al. / Engineering Geology 166 (2013) 7480(a)
Sche1Sample 2Porous stone 3Piston 4Load s
Valve 9Salt solution 10Nut 11Silicon oilbeginning stage of
hydration and rapidly reaches its rst peak, whichfollowed by an
intermediate period where the swelling pressure de-creases. After
that, the swelling pressure increases again and reachesits nal
steady-state value (the second peak). This observation is in
ac-cordance with the results reported by Villar and Lloret (2008)
and Yeet al. (2012). However, when the concentration of salt
concentrationsincreased to a relatively high level (N0.5 M), the
double-peak curvesof swelling pressure faded to single-peak ones.
This phenomenon
(b) Pictures Testing cell 2 Fresh/saline water conversion device
3 Pressure-volume controller 4Data
logger
Fig. 1. Setup for swelling pressure and saturated hydraulic
conductivity test.
Table 2Tests and selected solutions.
Sample Solutions
1 De-ionized water2 0.1 M NaCl3 0.5 M NaCl4 1.0 M NaCl5 2.0 M
NaCl6 0.1 M CaCl27 0.5 M CaCl28 1.0 M CaCl29 2.0 M CaCl2
Fig. 2. Inuence of concentrations of NaCl solutions on the
swelling pressure of GMZ01bentonite.
-
indicates that the concentration of solutions signicantly
inuences theswelling properties of the compacted GMZ01
bentonite.
This observation can be explained by the swelling process of
water in the interlayer space between the TOT montmorillonite
units.This amount of water may be not enough to form any DDL in
thesmall interlayer space (Pusch and Yong, 2006), but it can be
enoughto form some DDL in the interquasicrystal pores.
Consequently, thestructure of bentonite may partially rebuilt after
the initial collapseand swells again, leading to an increase of
swelling pressure up to amaximum constant value corresponding to
the second peak (stage IIIin Fig. 4).
In case of hydrating with relatively higher concentration
solutions(N0.5 M), swelling in stages I and II are similar to that
of hydratingwith low concentrations. It can also be observed that,
for all the tests,it takes about 10 h for swelling pressure to
reach its rst peak. This phe-nomenon may be explained that
development of swelling pressure atthis stage probably is governed
by the matric suction dissipation notthe chemical composition of
the inltrating solutions (Rao et al.,2006). According to the DDL
theory, the DDL thickness varies inverselywith the square root of
the concentration (Tripathy et al., 2004). Hence,higher
concentrations will cause a reduction in the DDL thickness
andconsequently a decrease of the repulsive forces between clay
particles(Yong and Warkentin, 1975; Mitchell, 1976). As a result,
the materialsundergo lower swelling (Karnland, 1997; Mata, 2003;
Castellanoset al., 2008). Therefore, after collapse of the soil
skeleton, high concen-tration of solutions diminishes the diffuse
double-layer swelling. Conse-
Fig. 3. Inuence of concentration of CaCl2 solutions on the
swelling pressure of GMZ01bentonite.
77C.-M. Zhu et al. / Engineering Geology 166 (2013)
7480compacted bentonite described in Fig. 4. Commonly, swelling of
benton-ite exposed towater or electrolytes is primarily on account
of twomech-anisms: the crystalline swelling and the diffuse
double-layer swelling(Madsen, 1989; Savage, 2005). The crystalline
swelling is caused by thehydration of exchangeable cations (K+,
Na+, Ca2+ and Mg2+) betweenmontmorillonite unit layers that have a
structurewith one alumina octa-hedral sheet sandwiched between two
silica tetrahedral sheets (TOT).After the adsorption of
maximumnumber of hydrates, surface hydrationbecomes less signicant
and diffuse double-layer repulsion becomes thegoverning swelling
mechanism (Bradbury and Baeyens, 2003).
In case of hydrating with low concentration solutions, after
com-pletion of the crystalline swelling, swelling pressure reaches
its rstpeak (stage I in Fig. 4). Followed by the swelling of
aggregates, thisinduces the collapse of the soil skeleton under
conned conditions,which characterized by the thick quasicrystals
split into thinner onesand ll into the macro-pores (inter-aggregate
pores), resulting in thedropping of the swelling pressure (from
stages I to II in Fig. 4).Then, the diffuse double-layer repulsion
dominates the swelling. Fordensely compacted bentonite, there is
only a small amount of adsorbedFig. 4. Conceptual diagrams of
constant-volume swelling process and microstructurequently,
swelling pressure will almost not increase and directly reachesits
nal stable value. Furthermore, this swelling pressure is mainly
in-duced by the crystalline swelling, while the double layer
repulsionmakes little contributions.
3.1.2. Impact of cation typesThe inuence of cation types on nal
swelling pressure is shown in
Fig. 5. It can be observed that, for a given concentration, the
swellingpressure of compacted GMZ01 bentonite hydrated with NaCl
solutionsis lower than that with CaCl2 solutions. The difference
depends on theconcentration of solutions. For low concentrations of
salt solutions, thedifference is small. On the contrary, for higher
concentrations, the swell-ing pressure with the low-valence salt
(NaCl) solutions is much lowerthan that with high-valence salt
(CaCl2) solutions. This phenomenonsuggests that theweakening effect
of Na+ on swelling pressure is great-er than that of Ca2+.
It is generally recognized that cation exchange is an important
factorinuencing the claywater interaction (Abdullah et al., 1999).
The cat-ion exchange is mainly controlled by the type, valence,
concentrationof compacted GMZ01 bentonite (Modied from Villar,
2002; Suzuki et al., 2005).
sw
-
particles in the relatively large pores in the upper part of the
soil sample.
Fig. 6. Inuence of concentration of NaCl solutions on the
hydraulic conductivity of GMZ01bentonite.
78 C.-M. Zhu et al. / Engineering Geology 166 (2013) 7480and
size of cations (Mata, 2003). The higher the valence, the higher
isthe replacing capacity of the cation. For cations with same
valence, thereplacing capacity increases with the size of cation
(Laine andKarttunen, 2010). A typical order for cation exchanging
capacity is:Na+ b K+ b Mg2+ b Ca2+ (Mitchell, 1976; Pusch, 2001;
Mata, 2003).So, when Nabentonite inltrated with calcium solutions,
sodium willbe replaced by calcium (Muurinen and Lehikonen, 1999;
Mata et al.,2005), resulting in the transformation from the
Nabentonite to a calci-um bentonite (Montes-H and Geraud, 2004;
Montes-H et al., 2005).
In present study,when the compactedGMZ01bentonite
samplewasinltratedwith CaCl2 solutions, someNa+ in the bentonitewas
gradual-ly replaced by Ca2+. Correspondingly, part of the
Nabentonite is thentransformed into a kind of Cabentonite, in which
Ca2+ becomes themain exchangeable cation. It is generally admitted
that the hydrationforces of Na+ and Ca2+ ions are different. The
number of interlamellarhydrated depends on the relative humidity
and the density of thecompacted bentonite. Provided that there is
no geometrical restraint,14 interlamellar hydrate layers can be
formed depends on the relativehumidity. Under constant volume
conditions, no more than twointerlamellar hydrate layers can be
formed in the densely compactedGMZ01 bentonite sample (1.70 Mg/m3)
tested in this study. When theadsorbed cation is Ca2+, the
thicknesses of interlamellar of the rstand the second hydrates are
3.89 and 2.75 , respectively. While forthe adsorbed cation Na+, the
thicknesses of interlamellar of the rstand the second hydrates are
3.03 and 3.23 , respectively (Pusch
Fig. 5. Comparison of inuence of cation types on the swelling
pressure of GMZ01bentonite.and Yong, 2006). This suggests that
Cabentonite has large basal spacethan that of Nabentonite.
Moreover, when Na+ is in the interlamellar,the coupling to water
molecules is probably weak and the cations rela-tively free to
move. While in Casmectite, the cations are strongly hy-drated and
the interlamellar complexes are rigid and stable. Thismeans that
the swelling pressure is higher for Casmectite than thatfor
Nasmectite with high bulk densities (Pusch and Yong,
2006).Therefore, the swelling pressure of bentonite inltratedwith
CaCl2 solu-tions is higher than that of bentonite inltrated with
NaCl solutions.
3.2. Hydraulic conductivity
3.2.1. Impact of concentrationsThe inuence of de-ionized water
and concentration of salt solu-
tions (NaCl and CaCl2) on the evolution of hydraulic
conductivity ofcompacted GMZ01 bentonite is shown in Figs. 6 and 7,
respectively. Itis observed that the hydraulic conductivity
decreases gradually overtime and becomes stable after 250 hour
inltration. This decrease canbe possibly attributed to the clay
particle movement (Ye et al., 2012).The hydrated clay particles
could move with inltration at the begin-ning of test and this
movement would lead to accumulation of clayAs a result, the
hydraulic conductivity decreases. When this processended, the
measured hydraulic conductivity becomes stable. Themaximum value
changes from 2.1 1013 m/s (inltrated with de-ionized water) to 8.2
1013 m/s (with 2.0 M NaCl solution) and4.5 1013 m/s (with 2.0 M
CaCl2 solution), respectively. The resultsindicate that the
hydraulic conductivity increases with the increase ofconcentration
of inltrating solutions. This observation is consistentwith that
reported by other researchers (Studds et al., 1998; Dixon,2000;
Mata, 2003; Suzuki et al., 2005; Villar, 2005; Karnland et al.,
2006).
Development of hydraulic conductivity with nal swelling
pressureof compacted GMZ01 bentonite testedwas plotted in Fig. 8.
Fig. 8 showsthat the hydraulic conductivity decreases with the
increase of swellingpressure. This phenomenon can be explained from
a microstructurallevel. In case of bentonite hydrating with low
concentration solutions,sufcient hydration leads to thick
quasicrystals splitting into severalthinner ones and yields
clogging of the macro-pores (inter-aggregatepores) (stage III in
Fig. 4), which work as main owing-channels.Consequently, the
hydraulic conductivity is relatively low. On thecontrary, when the
concentration of electrolyte increases, the diffusedouble-layer
swelling will be restricted, results in decreasing of theswelling
of clay particles. This would lead to decrease of inuence
ofhydration on macro-pores (stage II in Fig. 4). As a result, the
hydraulicconductivity increases as the concentration of electrolyte
increases.Fig. 7. Inuence of concentration of CaCl2 solutions on
hydraulic conductivity of GMZ01bentonite.
sw
sw
-
Fig. 8. Hydraulic conductivity vs. nal swelling pressures of
compacted GMZ01 bentonite.
79C.-M. Zhu et al. / Engineering Geology 166 (2013) 74803.2.2.
Impact of cation typesComparison of inuence of cation types on
hydraulic conductivity of
GMZ01 bentonite is shown in Fig. 9. It appears that the
hydraulic con-ductivity of GMZ01 bentonite is found to increase by
3.25 and 1.54times, when the concentration of NaCl and CaCl2
solutions increasefrom 0.1 M to 2.0 M. For a given concentration,
the values of hydraulicconductivity with different salt solutions
are different. Furthermore,the difference depends on the
concentration of the solutions. For lowconcentrations, the
difference is insignicant. However, as concentra-tion increases,
the difference increases signicantly.
Fig. 9 also shows that the hydraulic conductivity of GMZ01
bentoniteinltrated with NaCl solutions is higher than that
inltrated with CaCl2solutions at same concentrations. This may be
attributed to that, com-pare to CaCl2 solutions, inltration of NaCl
solutions leads to less clog-ging of macro-pores, which results in
a relatively higher hydraulicconductivity. This observation agrees
with the results reported byPusch (2001) and Castellanos et al.
(2008) who also found that the hy-draulic conductivity of bentonite
increases faster when sodium is thepredominant cation in the
inltrating solution.
4. Conclusions
Inuence of the salinity of inltration solutions on the swelling
pres-sure and hydraulic conductivity of compacted GMZ01 bentonite
at aninitial dry density of 1.7 Mg/m3 was investigated by means of
swellingFig. 9. Comparison of inuence of cation types on hydraulic
conductivity of GMZ01bentonite.and permeability tests, in which
de-ionized water and NaCl and CaCl2solutions of different
concentrations were used.
Results obtained indicate that the salinity of inltrating
solutionssignicantly inuences the swelling pressure of GMZ01
bentonite. Theswelling pressure decreases with the increase of
concentration of inl-trating solutions and the degree of impact
decreases with the increaseof concentration. For a given
concentration, the swelling pressure ofGMZ01 bentonite inltrated
with CaCl2 solution is higher than thatwith NaCl solution. The
higher the concentration of inltrating solutionis, the shorter it
takes for the swelling pressure to reach its stable state.
The hydraulic conductivity of GMZ01 bentonite increases with
theincrease of concentration of inltrating solutions. For high
concentra-tions, the inuence of Na+ on the hydraulic conductivity
of GMZ01 ben-tonite is greater than that of Ca2+. This can be
explained that inltrationof NaCl solutions induces less clogging of
macro-pores, which results ina relatively higher hydraulic
conductivity.
Acknowledgments
The authors are grateful to the National Natural Science
Foundationof China (Projects No. 41030748, 41272287), China Atomic
Energy Au-thority (Project [2011]1051) for the nancial supports.
This work wasalso conducted within a Program for Changjiang
Scholars and Innova-tive Research Team in University (PCSIRT,
IRT1029).
References
Abdullah, W.S., Alshibli, K.A., Al-Zou'bi, M.S., 1999. Inuence
of pore water chemistry onthe swelling behavior of compacted clays.
Appl. Clay Sci. 15, 447462.
Bradbury, M.H., Baeyens, B., 2003. Porewater chemistry in
compacted re-saturatedMX-80bentonite. J. Contam. Hydrol. 61,
329338.
Castellanos, E., Villar, M.V., Romero, E., Lloret, A., Gens, A.,
2008. Chemical impact on thehydro-mechanical behavior of
high-density FEBEX bentonite. Phys. Chem. Earth. 33,S516S526.
Dixon, D.A., 2000. Pore Water Salinity and the Development of
Swelling Pressure inBentonite-Based Buffer and Backll Materials.
POSIVA Report 2000-04. Posiva Oy,Helsinki, Finland.
Guo, Y.H., Yang, T.X., Liu, S.F., 2001. Hydrogeological
characteristics of Beishan preselectedarea, Gansu province for
China's high-level radioactive waste repository. UraniumGeol. 17
(3), 184189.
Herbert, H.-J., Kasbohm, J., Sprenger, H., Fernndez, A.M.,
Reichelt, C., 2008. Swelling pres-sures of MX-80 bentonite in
solutions of different ionic strength. Phys. Chem. Earth33,
S327S342.
Karnland, O., 1997. Bentonite Swelling Pressure in Strong NaCl
Solutions: Correlationbetween Model Calculations and Experimentally
Determined Data. SKB TechnicalReport 97-31. Swedish Nuclear Fuel
and Waste Management Co., Stockholm.
Karnland, O., Olsson, S., Nilsson, U., 2006. Mineralogy and
Sealing Properties of VariousBentonites and Smectite-Rich Clay
Materials. SKB TR-06-30. Swedish Nuclear Fueland Waste Management
Co., Stockholm, Sweden.
Komime, H., Yasuhara, K., Murakami, S., 2009. Swelling
characteristics of bentonites inarticial seawater. Can. Geotech. J.
46 (2), 177189.
Laine, H., Karttunen, P., 2010. Long-Term Stability of Bentonite
A Literature Review.POSIVA Report 2010-53. Posiva Oy, Helsinki,
Finland.
Lee, J.O., Lim, J.G., Kang, I.M., Kwon, S., 2012. Swelling
pressures of compacted Cabentonite.Eng. Geol. 129130, 2026.
Madsen, F.T., Mller-VonMoos, M., 1989. The swelling behaviour of
clays. Appl. Clay Sci. 4,143156.
Mata, C., 2003. Hydraulic Behaviour of Bentonite Based Mixtures
in Engineered Barriers:The Backll and Plug Test at the sphrl
(Sweden). (Ph. D. Thesis) UniversitatPolite`cnica de Catalunya,
Barcelona.
Mata, C., Guimares, L., do, N., Ledesma, A., Gens, A., Olivella,
S., 2005. A hydro-geochemicalanalysis of the saturation process
with salt water of a bentonite crushed granite rockmixture in an
engineered nuclear barrier. Eng. Geol. 81, 227245.
Mitchell, J.K., 1976. Fundamentals of Soil Behavior. John Wiley
& Sons, New York.Montes-H, G., Geraud, Y., 2004. Sorption
kinetic of water vapour of MX80 bentonite
submitted to different physical-chemical and mechanical
conditions. Colloids Surf.,A Physicochem. Eng. Asp. 235, 1723.
Montes-H, G., Fritz, B., Clement, A., Michau, N., 2005.
Modelling of geochemical reactionsand experimental cation exchange
inMX-80 bentonite. J. Environ.Manage. 77, 3546.
Muurinen, A., Lehikonen, J., 1999. Porewater chemistry in
compacted bentonite. Eng.Geol. 54, 207214.
Pusch, R., 2001. Experimental Study of the Effect of High
Porewater Salinity on the Phys-ical Properties of a Natural
Smectitic Clay. SKB Technical Report TR-01-07, Stockholm.
Pusch, R., Yong, R.N., 2006. Microstructure of Smectite Clays
and Engineering Perfor-mance. Taylor & Francis, London and New
York.
Pusch, R., Karnland, O., Hkmark, H., 1990. GMM-a General
Microstructural Model forQualitative and Quantitative Studies on
Smectite Clays. SKB Technical Report 90-43,
Stockholm.
-
Rao, S.M., Thyagaraj, T., Thomas, H.R., 2006. Swelling of
compacted clay under osmoticgradients. Geotechnique 56 (10),
707713.
Savage, D., 2005. The Effects of High Salinity Groundwater on
the Performance of ClayBarriers. SKI Report 54.
Siddiqua, S., Blatz, J., Siemens, G., 2011. Evaluation of the
impact of pore uid chemistryon the hydromechanical behaviour of
clay-based sealing materials. Can. Geotech. J.48, 199213.
Studds, P.G., Stewart, D.I., Cousens, T.W., 1998. The effects of
salt solutions on the propertiesof bentonitesand mixtures. Clay
Minerals 33, 651660.
Suzuki, S., Prayongphan, S., Ichikawa, Y., Chae, B., 2005. In
situ observations of the swellingof bentonite aggregates in NaCl
solution. Appl. Clay Sci. 29, 8998.
Tripathy, S., Sridharan, A., Schanz, T., 2004. Swelling
pressures of compacted bentonitesfrom diffuse double layer theory.
Can. Geotech. J. 41, 437450.
Villar, M.V., 2002. Thermo-hydro-mechanical Characterisation of
a Bentonite from Cabo DeGata. A Study Applied to the Use of
Bentonite as Sealing Material in High LevelRadioactive Waste
Repositories. Publicacin Tcnica ENRESA 01/2002, Madrid (44
pp.).
Villar, M.V., 2005. Thermo-hydro-mechanical characterization
performed at CIEMAT inthe context of the prototype project. Inf. Tc
Ciemat 1053 (Madrid).
Villar, M.V., Lloret, A., 2004. Inuence of temperature on the
hydro-mechanical behaviourof a compacted bentonite. Appl. Clay Sci.
26, 337350.
Villar, M.V., Lloret, A., 2008. Inuence of dry density and water
content on the swelling ofa compacted bentonite. Appl. Clay Sci.
39, 3849.
Wen, Z.J., 2006. Physical property of china's buffer material
for high-level radioactivewaste repositories. Chin. J. Rock Mech.
Eng. 25, 794800 (in Chinese).
Wersin, P., Johnson, L.H., McKinley, I.G., 2007. Performance of
the bentonite barrier attemperatures beyond 100 C: a critical
review. Phys. Chem. Earth. 32, 780788.
Ye, W.M., Cui, Y.J., Qian, L.X., Chen, B., 2009. An experimental
study of the water transferthrough conned compacted GMZ bentonite.
Eng. Geol. 108, 169176.
Ye,W.M., Chen, Y.G., Chen, B., Wang, Q., Wang, J., 2010.
Advances on the knowledge of thebuffer/backll properties of heavily
compacted GMZ bentonite. Eng. Geol. 116 (12),1220.
Ye, W.M., Wan, M., Chen, B., Chen, Y.G., Cui, Y.J., Wang, J.,
2012. Temperature effectson the swelling pressure and saturated
hydraulic conductivity of the compactedGMZ01 bentonite. Environ.
Earth Sci. http://dx.doi.org/10.1007/s12665-012-1738-4.
Yong, R.N., Warkentin, B.P., 1975. Soil Properties and
Behaviour. Elsevier, Amsterdam.
80 C.-M. Zhu et al. / Engineering Geology 166 (2013) 7480
Influence of salt solutions on the swelling pressure and
hydraulic conductivity of compacted GMZ01 bentonite1.
Introduction2. Experimental investigations2.1. Materials2.2. Test
apparatus2.3. Test procedures2.3.1. Sample preparation2.3.2.
Swelling pressure tests2.3.3. Hydraulic conductivity tests
3. Test results and discussions3.1. Swelling pressure3.1.1.
Impact of concentration3.1.2. Impact of cation types
3.2. Hydraulic conductivity3.2.1. Impact of concentrations3.2.2.
Impact of cation types
4. ConclusionsAcknowledgmentsReferences