The Effect of Different Types of Water on the Swelling Behaviour
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Transcript of The Effect of Different Types of Water on the Swelling Behaviour
ORIGINAL PAPER
The effect of different types of water on the swelling behaviourof expansive clays
Isık Yilmaz • Marian Marschalko
Received: 22 March 2013 / Accepted: 20 March 2014 / Published online: 8 April 2014
� Springer-Verlag Berlin Heidelberg 2014
Abstract In the design of foundations of structures,
especially light buildings, on clayey soils, the main soil
behaviours to be considered are swelling properties and
surface heave. Therefore, determination of swelling prop-
erties by means of swell percent and maximum swell
pressure as well as estimation of the surface is very
important in the investigation of such soils and light
structures on them. In order to obtain the swelling
parameters of clayey soils, experimental laboratory tests
were carried out and standardised. Distilled water is gen-
erally used during these experimental tests; however, the
soil in situ interacts with different types of water having
different water chemistries. Therefore, the swelling
behaviour of expansive soils tested with distilled water
would naturally be different from the behaviour of
expansive soils tested with different water types and
chemistries. For this reason, it was anticipated that deter-
mination of the realistic swell behaviour in laboratory
experiments requires the use of the same water as in the
in situ condition. In this article, the effect of the water type
and chemistry on the swelling behaviour of the clays was
investigated by testing the clay samples with eight different
types of water collected from the sea, river, lake and dif-
ferent rock formations. The main result of this research was
that the anticipated clay swell percentages and pressures
for different types of water were lower than for the distilled
water routinely used in testing.
Keywords Clay soils � Swelling � Swell potential �Water
type and chemistry
Introduction
Damage and movements sourced from expansive clays
generally occur relatively slowly and do not cause dramatic
hazards such as hurricanes, earthquakes, etc. Sometimes
the impacts of expansive soils are of minor maintenance
and aesthetic concerns, but often they are much worse,
even causing major structural distress (Coduto 1999).
Many buildings are constructed with foundations that
are inadequate for the soil conditions existing on the site.
Because of the lack of suitable land, homes are often built
on marginal land that has insufficient bearing capacity to
support the substantial weight of a structure. Land becomes
scarce with the growth of cities, and it often becomes
necessary to construct buildings and other structures on
sites with unfavourable conditions. One of the most
important characteristics of clayey soils is their suscepti-
bility to the volume change caused by swelling and
shrinkage. Such volume changes can give rise to ground
movements that can damage buildings (Bell and Maud
1995).
Swelling percent and especially swelling pressures of
clayey soils must be calculated; in particular, surface heave
must be estimated depending on the calculated swelling
parameters before construction of light-weight buildings.
On the other hand, calculation of the swelling potential also
has great importance when excavations (tunnels, trenches,
pits, etc.) are likely to be left open for significant periods of
I. Yilmaz (&)
Department of Geological Engineering, Faculty of Engineering,
Cumhuriyet University, 58140 Sivas, Turkey
e-mail: [email protected]
M. Marschalko
Faculty of Mining and Geology, Institute of Geological
Engineering, VSB-Technical University of Ostrava, 17
Listopadu 15, 708 33 Ostrava, Czech Republic
123
Bull Eng Geol Environ (2014) 73:1049–1062
DOI 10.1007/s10064-014-0598-4
time. As stated by Karacan and Yilmaz (1996), lateral
pressures and floor heave will occur during excavation
depending on the groundwater level changes around the
excavation and swell potential of the clay.
The swelling potential of expansive clayey soils depends
on the reduction of the overburden stress, unloading con-
ditions, exposure to water and increases in moisture con-
tent. Bell and Maud (1995) found that low-rise buildings
are particularly vulnerable to ground movements because
they generally do not have sufficient weight or strength to
resist them. Geotechnical engineers have long recognised
that swelling of expansive soils caused by moisture varia-
tion may result in considerable distress and consequently in
severe damage to the overlying structures (Basma 1991;
Yilmaz 2006, 2008, 2009; Yilmaz and Civelekoglu 2009;
Yilmaz and Kaynar 2011). Lightweight buildings are
especially prone to damage from expansive soils. The
magnitude of heaving and shrinking generally varies across
the building, thus causing problems similar to those asso-
ciated with excessive differential settlements.
The swelling properties of bentonite have been investi-
gated by a number of authors. Evans and Quigley (1992)
investigated the effect of leaching from solid waste on the
permeability and swell percent of sand-bentonite mixtures.
According to their results, leaching caused an increase in
the permeability and decrease in the swelling. Simons and
Reuter (1985) similarly investigated the effect of leaching
from wastes and absorption, and showed the traces of the
changes in ions and electrostatic forces. Di Maio (1996)
reported an increase in the free swell of bentonite by
interaction with the water after bentonite was kept in NaCl,
KCl and CaCl2 solutions. It was also found that the
exchange of Na? was a reversible reaction, while the
exchange of Ca2? or K? was permanent.
Changes in the chemical composition of the pore fluid
exert different effects on clays. They may cause exchanges
of cations between the mineralogical units, variations in the
electrochemical forces acting between different platelets
and variations in the osmotic pressure. On the microscopic
scale, the distance between different unit layers depends on
the valence, dimension and hydration state of the interlayer
cations. On the mesoscopic scale, the ionic strength of the
solution controls the repulsion forces between different
particles as well as the osmotic pressure in the micro pores.
At the macroscopic scale, the distance between peds is
such that the repulsion effect is lost, while the effect due to
changes in the bulk osmotic pressure remains (Musso et al.
2003). Yong and Warkentin (1975) determined a decrease
in swell potential by increasing salt concentrations in clays
containing univalent exchangeable cations. Basma and Al-
Sharif (1994) then reported that the effect of the salt con-
centration on the pores starts to decrease by exceeding a
certain degree of concentration. Jullien et al. (2002)
investigated the role of solute chemistry on clay perme-
ability, swelling strain, porosity and the retention curve by
using the clays of Ca French expansive clay known as Fo–
Ca. They also investigated the permeability as well as
swelling strain changes along soaking paths with copper
concentration with respect to the two sets of boundary
conditions. Moreover, the ion sorption ability of the Fo-Ca
was studied by means of leachate analyses. Porosity and
retention curves were also given after testing with respect
to copper concentrations. They found significant changes
resulting from the copper solute injection for all the
material parameters.
The effect of the salinity of the pore water in clays
has been researched and reported by many authors, such
as Petrov and Rowe (1997), Alawaji (1999), Shackelford
et al. (2000), Jo et al. (2001, 2004, 2005), Kolstad et al.
(2004), Lee and Shackelford (2005), Lee et al. (2005),
Mishra et al. (2005). A common finding of the research
was that salt solutions cause a collapse in the clay
structure, a decrease in the thickness of the diffusion
double layer (DDL), an increase in hydraulic conduc-
tivity and a decrease in swell potential. Sridharan et al.
(1990) found that increases in the electrolyte concentra-
tion in pore water caused an increase in the free swell
index of kaolinite-type clay, a decrease in smectite-type
clay and a decrease in smectite-type clay. They
explained this result as the flocculation promoted by the
salinity and decrease in thickness of the DDL in smec-
tite-type clay. According to Mowafy et al. (1985), elec-
trolytes in the pore water of clay cause some changes in
the surface of clay particles, and an increase in salinity
promotes flocculation. Therefore, the total surface area
and quantity of the absorbed water decrease by
increasing the grain size in flocculated clay. These are
the main causes of reduced swell potential in clays. The
authors especially pointed out that the exchange of cat-
ions on the surface of clay particles with cations of pore
water causes a decrease in swell potential by blocking
the water inflow into the sheets. Karımpour (2002) also
reported similar results, describing that flocculation as a
result of the water salinity breaks the structure of clay
and significantly affects the hydraulic conductivity, and
the swell potential is reduced.
The literature reviewed above shows that the swelling
potential of clay varies with water chemistry. In addition,
it is very well known that the chemistry of water is
significantly influenced by interactions with bedrocks
depending on the residence time and solubility of rocks.
Whilst it is possible to find extensive literature related to
the effects of the water chemistry on the swell potential
of clays, research aiming to represent the effect of the
different types of water on the swell potential of the
clays is not widespread. In order to obtain swelling
1050 I. Yilmaz, M. Marschalko
123
parameters (swell percent and swell pressure) of expan-
sive clays, laboratory experiments have been carried out
and standardised. Distilled water is generally used in the
experiments; however, in situ the clays are subject to
interaction with different types of water with different
water chemistries such that the swelling behaviour of
expansive clays tested with distilled water would natu-
rally be different from that of expansive clays tested
with different water types and chemistries. Moreover,
water chemistries show variation with proximity to the
sea and/or lakes where sea and/or lake water intrusion
into the soil exists. In this article, the effect of the water
types and chemistries on the swelling behaviour of
expansive clays was investigated. The main result of this
research was that the anticipated realistic clay swelling
percent and pressures for clays tested with different types
of water were lower than for distilled water-based
experiments.
Bentonite used in the experiments
Bentonite samples were taken from 25 km north of
Resadiye (Fig. 1). The bentonite used in the tests is a
natural, pure and sodium-based untreated material. It con-
tains dominantly Na-Smectite (montmorillonite) clay
mineral having a very high swelling capacity. Small
amounts of feldspar, quartz, calcite and opal-CT are also
observed. Figure 2 shows a characteristic XRD diffracto-
gram. XRD-whole rock powder results and the chemical
composition of bentonite are shown in Table 1.
As quoted by Yalcin and Gumuser (2000), smectite
aggregates are composed of bent/folded, thin, subhedral
lamellae, as shown in scanning electron microscopy (SEM)
micrographs of the bentonite (Fig. 3a). These loosely
compacted, folded aggregates (Fig. 3b) resemble the
Wyoming type (Grim and Guven 1978) with a ‘‘cornflake’’
texture as described by Keller (1978). The smectite
Fig. 1 Location map of
bentonite used in the study
Fig. 2 Characteristic XRD
graphs of bentonite used
Swelling behaviour of expansive clays 1051
123
lamellae are *2–5 lm long, and they are associated with
small amounts of short prismatic clinoptilolite (Yalcin and
Gumuser 2000).
Samples for free swell and swelling pressure tests were
obtained from the samples compacted at optimum water
content. In order to obtain almost the same samples for all
tests, standard Proctor tests in accordance with the appro-
priate international standard of ASTM D-698 (1994) were
first conducted on the bentonite, and optimum water con-
tent was determined as 41.8 % (Fig. 4).
Different types of water used in the experiments
Eight different types of water used in this study were
collected from three different seas (the Mediterranean,
Aegean and Black Seas), a river (Kizilirmak), a lake (Deli
Ilyas) and three different rock formations (Tecer lime-
stones, Kosedag volcanics and gypsum) in Turkey
(Fig. 5). Table 2 shows the abbreviations for the water
types used in the figures and tables. The results of the
water chemistry analyses of the water samples are given
in Table 3.
According to the results of the water chemistry analyses,
the most saline water is that from the Mediterranean Sea
(34.89 %), and all sea water samples are rich in salt con-
tent. While sea water salinity changes from 15.03 to
34.89 %, the salinity varies between 0.03 and 1.21 % for
the other water samples.
The pH values were similar for all water samples, and
they were evaluated as alkaline. Electrical conductivity
(EC) values of the water samples were determined: higher
EC values (from 24,760 to 53,100 lS/cm) were obtained
for sea water samples, while the EC ranged between 94 and
225 lS/cm in other water types, depending on their
salinities.
Very high ion concentrations of sodium, calcium,
chlorine, sulphate and magnesium were obtained from
samples of the Mediterranean and Aegean Sea; however,
ion concentrations in Black Sea water were relatively low.
While the carbonate concentrations were very high in water
samples from the Black Sea and Mediterranean Sea, con-
centrations of carbonate in the Aegean Sea and lake water
were closer to them. Carbonate was not found in other
water samples.
Ion concentrations of sodium, calcium, chloride and
sulphate in water samples collected from the Kizilirmak
River and gypsum formations were relatively lower than
sea water samples; concentrations were higher than in the
other water samples. The lowest values of all ion concen-
trations, salinity and EC were obtained from water samples
collected from Tecer and Kosedag, but these values were
higher in Tecer than Kosedag.
Table 1 XRD (whole rock powder) analysis results and chemical
composition of bentonite
XRD
Na-smectite (%) 81
Feldspar (%) 7
Quartz (%) 2
Calcite (%) 2
Opal-CT (%) 8
Chemical composition (after Yalcin and Gumuser 2000)
Silica, as SiO2 (%) 60.11
Titanium, as TiO2 (%) 0.39
Alumina, as Al2O3 (%) 18.77
Total ferric oxide, as RFe2O3 (%) 4.82
Manganese, as MnO (%) 0.054
Magnesium, as MgO (%) 2.38
Calcium, as CaO (%) 1.03
Sodium, as Na2O (%) 3.46
Potassium, as K2O (%) 1.75
Phosphorus, as P2O5 (%) 0.086
Loss on ignition (%) 6.34
Fig. 3 Scanning electron micrographs: a smectite lamelle and short prismatic clinoptiloties; b loose packing, folded-lamellar smectite
aggregates (after Yalcin and Gumuser 2000)
1052 I. Yilmaz, M. Marschalko
123
The Schoeller semi-logarithmic plot allows representa-
tion of major ion analyses to demonstrate different hyd-
rochemical water types on the same diagram. This type of
graphical representation has the advantage that, unlike the
trilinear diagrams, actual sample concentrations are dis-
played and compared. The Piper plot reveals useful prop-
erties and relationships for large sample groups. The main
purpose of the Piper diagram is to show clustering of data
points to indicate samples that have similar compositions.
Schoeller and Piper diagrams (Figs. 6, 7) were drawn by
using the software packages of RockWare Aq-QA, version
1.1.1 (1.1.5.1) (2006).
According to the evaluation of the semi-logarithmic
Schoeller diagram (Fig. 6), the three sea water samples are
similar. As seen in Table 4, dominant ions in sea water
samples were Na? and Cl-, while Ca2? ? HCO3- were
dominant in lake, Tecer and Kosedag water samples.
Na?? SO42- and Ca2? ? SO4
2- ions were respectively
dominant in the Kizilirmak River and gypsum formation
water samples.
Water samples were classified according to their posi-
tion on the Piper diagram (Fig. 7). Sea water samples
(Mediterranean, Aegean and Black Seas) were classified as
sodium/potassium and chloride type, whereas gypsum
formation water was classified as calcium and sulphate
type. While the water samples collected from Tecer and
Kosedag were classified as calcium and bicarbonate type,
Deli Ilyas Lake water was magnesium and bicarbonate
type. However, the Kizilirmak River water does not have a
dominant type.
Experimental procedures
Many factors affect the swell potential of the clays. These
factors were classified in three main groups by Nelson and
Miller (1992):
1. Soil properties (mineralogy, chemistry of pore water,
soil fabric and structure, soil suction, plasticity and dry
unit weight).
2. Environmental factors (initial water content and
changes in water content).
3. Stress conditions (pre-loading pressure, in situ condi-
tions and soil profile, surcharge loads).
In this study, mineralogy, soil fabric and structure, soil
suction, plasticity and dry unit weight were fixed by using
the same bentonite samples in all tests. Initial water con-
tents and changes in the water content were similar because
Fig. 4 Compaction curve of the bentonite showing optimum water
content and maximum dry unit weight
Fig. 5 Location map of water samples used in the study
Swelling behaviour of expansive clays 1053
123
the same testing conditions were applied in all tests. The
standard compaction of all samples in the same water
content allowed obtaining samples having the same pre-
loading pressures. Only the chemistry of pore water was
changed in the tests by using different types of water
samples as the main aim of this study.
In order to determine the swelling percent of the
bentonite used in the study, free swell tests were carried
out in accordance with the appropriate International
Standard ASTM D-4546 (1994). A 0.7-kPa pre-loading
pressure and samples with a 75-mm radius were used in
the tests. The sample in the ring was placed between two
porous plates, loaded with 0.7 kPa, and the cell was fully
filled with water. After the specimen had been allowed to
swell, readings of the dial gauge were periodically
recorded (10–15–30 s, 1–2–4–6–8–24–26–28–30–32–
Table 2 Descriptions of the water samples used in the study
Sample
acronym
Sample name Water type
AD Mediterranean Sea water
ED Aegean Sea water
KD Black Sea Sea water
KZRMK Kizilirmak River water
JPS Gypsum Water from a gypsum
formation
GOL Deli Ilyas Lake water
TCR Tecer Water from a limestone
formation
KSD Kosedag Water from volcanics
SAF Distilled
water
Table 3 Results of the water chemistry analyses
Sample pH EC Salinity Ca Mg Na K Cl SO4 HCO3
AD 7.73 53,100 34.89 763.73 1,669.6 12,364 577.13 22,547 2,750.6 149.51
ED 7.57 50,950 33.45 695.38 1,606.8 11,400 515.75 20,794 2,530.4 155.49
KD 7.58 24,760 15.03 342.88 695.55 4,897 158.97 8,698 1,086.33 152.5
KZRMK 7.74 2,520 1.21 214.7 29.52 238 6.05 349.7 454.6 254.2
JPS 7.45 1,970 1 285.07 36.84 58.04 2.89 150.56 445.19 245.2
GOL 8.16 544 0.26 55.93 43.8 10.65 2.46 6.8 135.2 203.3
TCR 8.10 325 0.15 46.9 11.01 6.88 0.84 5.29 16.75 167.5
KSD 7.62 94 0.03 11.65 2.36 2.48 0.75 1.19 2.5 50.71
EC (lS/cm), tuzluluk (%), ion concentration (ppm)
Fig. 6 Semi-logarithmic
Schoeller diagram
1054 I. Yilmaz, M. Marschalko
123
48–50–52–54–56–58–72 h) up to 72 h (3 days); S% ver-
sus time graphs were drawn. The swell percent (S%) was
then calculated as an increase in the height in relation to
the original thickness of the specimen.
Numerous laboratory swelling tests have been reported
for measurement of the swelling pressure of an expansive
soil. These test methods generally involve the use of a
conventional one-dimensional oedometer apparatus and are
generally determined in the laboratory. Swell is determined
by subjecting the laterally confined soil specimen to a
constant vertical pressure and by giving both the top and
bottom of the specimen access to free water (usually dis-
tilled) to cause swell. The swell pressure is determined by
subjecting the laterally confined soil specimen to increas-
ing vertical pressures, following inundation, to prevent
swell.
In this study, a one-dimensional oedometer apparatus
was used for measurement of the swell pressures. Periodic
measurement of increasing pressures was carried out up to
72 h, and swell pressure (SP) versus time (t) graphs were
plotted. The swell percent (S%) was then calculated as an
increase in height in relation to the original thickness of the
specimen. The peak values were determined from the
graphs as swell pressures of the related specimens.
A clay sample was first tested with distilled water,
and the swell percent and swell pressure were obtained
(Fig. 8). The swell percent was found to be 65 % and
the swell pressure 269.86 kPa for distilled water-based
tests. The clay sample was then tested by using different
water samples types, and the results were compared with
those from the distilled water-based test. Swell tests with
different types of water were performed after clay
Fig. 7 Piper diagram
Table 4 Ion orders in water
samples according to Schoeller
diagram
Sample Dominant ions Cations Anions
AD Na? ? Cl- r(Na??K?) [ r(Mg2?) [ r(Ca2?) r(Cl-) [ r(SO42-) [ r(HCO3
-)
ED Na? ? Cl- r(Na??K?) [ r(Mg2?) [ r(Ca2?) r(Cl-) [ r(SO42-) [ r(HCO3
-)
KD Na? ? Cl- r(Na??K?) [ r(Mg2?) [ r(Ca2?) r(Cl-) [ r(SO42-) [ r(HCO3
-)
KZRMK Na? ? SO42- r(Na??K?) [ r(Ca2?) [ r(Mg2?) r(SO4
2-) [ r(Cl-) [ r(HCO3-)
JPS Ca2? ? SO42- r(Ca2?) [ r(Na??K?) [ r(Mg2?) r(SO4
2-) [ r(HCO3-) [ r(Cl-)
GOL Ca2? ? HCO3- r(Ca2?) [ r(Mg2?) [ r(Na??K?) r(HCO3
-) [ r(SO42-) [ r(Cl-)
TCR Ca2? ? HCO3- r(Ca2?) [ r(Mg2?) [ r(Na??K?) r(HCO3
-) [ r(SO42-) [ r(Cl-)
KSD Ca2? ? HCO3- r(Ca2? [ r(Na??K?)) [ r(Mg2?) r(HCO3
-) [ r(SO42-) [ r(Cl-)
Swelling behaviour of expansive clays 1055
123
samples soaked in water had been kept for 3 days in
desiccators.
Results
A significantly lower swell percent and pressure were
observed in clay as a result of experiments carried out
using the three sea water samples. Respective values of the
swell percent of Mediterranean, Aegean and Black Sea
samples used in the tests were 5.19, 5.48 and 11.11 %
(Fig. 9). Swell pressures for Mediterranean, Aegean and
Black Sea samples were 23.56, 24.69 and 25.35 kPa,
respectively (Fig. 10).
When the values were compared with the tests under-
taken with distilled water, the decrease in free swell in
Mediterranean, Aegean and Black Sea samples was
determined to be 92.02, 91.60 and 82.91 %, respectively.
Similarly, respective swell pressures were decreased to
90.8, 91.2 and 90.6 % in tests of clay samples mixed with
Mediterranean, Aegean and Black Sea samples.
As can be seen from the S% and SP versus time graphs
given in Figs. 9 and 10, higher decreases were obtained
from tests undertaken with Mediterranean and Aegean Sea
water samples; however, they were almost the same. The
results obtained from the Black Sea water-based tests were
relatively higher than the others.
The main characteristics of the three water samples
collected from seas are their higher values of salinity, EC
and ion concentrations than other water samples used in the
tests (Table 2). Especially the higher EC and salinity val-
ues of the seawater samples are important because of their
effects on the swell potentials of clay samples. The
respective EC and salinity values of Mediterranean,
Aegean and Black Sea water samples are 53,100 lS/cm—
34.89 %, 50,950 lS/cm—33.45 % and 24,760 lS/cm—
15.03 %. According to the salinity classification suggested
by Lewis (1982) (Table 5), seawater samples used in this
study were classified as ‘‘saline water.’’
Respective values of swell percents of 26.48 and
33.85 % were obtained using water samples from the Ki-
zilirmak River and gypsum rock. Swell pressures were
found to be 173.5 and 186.93 kPa for the Kizilirmak River
and gypsum, respectively (Figs. 11, 12). Both of the water
samples reduced the swell potential of clays, and the
comparison of these values with the distilled water sample
test results showed that the loss in S% and SP for the
Kizilirmak River and gypsum rock was 59.26 and 35.71,
47.92 and 30.73 %, respectively.
Water samples collected from the Kizilirmak River and
gypsum rock were found to be almost similar depending on
the interaction between the river and gypsum rocks
(especially in the river stretch between the Hafik and Zara
districts). While the EC and salinity values, calcium,
magnesium, sulphate and bicarbonate concentrations of
these two water samples from the Kizilirmak River and
gypsum rock were considerably lower than in the sea water
samples, they were significantly higher than in the others.
Fig. 8 a S% and b swell
pressure versus time graphs of
the tests for distilled water use
1056 I. Yilmaz, M. Marschalko
123
The two water samples were classified as ‘‘brackish water’’
according to the salinity classification suggested by Lewis
(1982) (Table 5).
The evaluation of the results obtained from swelling
tests with distilled water and lake water samples (Fig. 13)
showed the respective values of the decrease in the
swelling percent and pressures to be from 65 % and
269.86 kPa to 40.61 % and 200.11 kPa. The respective
losses of swelling percent and pressures were calculated as
37.52 and 25.84 % by comparing the distilled water- and
lake water-based tests.
The lake water sample used in the tests had lower EC
values, salinity and ion concentrations than water samples
collected from the seas, Kizilirmak River and gypsum rock,
while higher than the others. According to the salinity
classification of Lewis (1982) (Table 5), the water sample
was classified as ‘‘fresh water.’’
A relatively low decrease in swell percent and pressure
was observed in the clay as a result of experiments carried out
using the water sample taken from Tecer. Respective values
of swell percent and swell pressure were 47.39 % and
215.99 kPa, respectively (Fig. 14). When the values were
compared with the distilled water tests, decreases in free
swell and swell pressures as percent were 27.09 and 19.96 %.
The least mineralised water was the Kosedag water
according to the EC, salinity and ion concentration. The
swell percent and swell pressure values obtained were very
close to the values obtained from the distilled water used in
the tests. The respective percents of free swell and swell
pressure loss were 13.49 and 15.14 %. The free swell value
was calculated as 56.23 %, while the swell pressure was
229 kPa (Fig. 15).
Discussions and conclusions
In this article, the influence of water type on the
swelling potential of clays was presented. The following
main discussions and conclusions can be drawn from this
study.
The four factors may generally contribute to the
reduction of free swell and swell pressure water used in the
tests.
Fig. 9 S% versus time graphs
obtained from the free swell
tests using the sea water
samples
Fig. 10 SP versus time graphs
obtained from the swell pressure
tests using the sea water
samples
Table 5 Water salinity classification (Lewis 1982)
Fresh Brackish Saline Brine
\0.5 % 0.5–30 % 30–50 % [50 %
Swelling behaviour of expansive clays 1057
123
1. The electrolyte concentration in sea water may reduce
the swell potential by shrinking the diffuse double
layer (DDL) (Sridharan et al. 1990).
2. By considering the results of Yong and Warkentin
(1975), it is possible to say that the high salt
concentration in water may affect the clay’s physical
Fig. 11 S% versus time, SP
versus time graphs obtained
from the swell tests using water
samples collected from the
Kizilirmak River
Fig. 12 S% versus time, SP
versus time graphs obtained
from the swell tests using water
samples collected from gypsum
rock
1058 I. Yilmaz, M. Marschalko
123
Fig. 13 S% versus time, SP
versus time graphs obtained
from the swell tests using the
water samples collected from
lake
Fig. 14 S% versus time, SP
versus time graphs obtained
from the swell tests using water
samples collected from Tecer
Swelling behaviour of expansive clays 1059
123
properties by causing fine particles to bind together
into aggregates, which are known as flocculation. The
flocculation may cause a reduction of the specific
surface area, and the free swell and swell pressure may
decrease.
3. Cation exchange between sea water and clay may
prevent water from entering between the layers, and
the swell potential may decrease. As reported by Lee
et al. (2005) and Mishra et al. (2005), a decrease in the
thickness of the DDL is observed after the collapse of
the clay structure caused by salt solutions, and the
swell potential is decreased.
4. Moreover, the very high sodium concentrations in sea
water samples may cause replacement of divalent ions
such as calcium, which tends to reduce the DDL.
Alawaji (1999) also pointed out that the swell potential
decreases with increased sodium concentration in the
liquid.
Determination of the swell percent and pressure of
clayey soils is an important means of predicting the
behaviour of clays by means of explanation and prediction
of the behaviour of clays. One of the most important
characteristics of clayey soils is their susceptibility to
Fig. 15 S% versus time, SP
versus time graphs obtained
from the swell tests using water
samples collected from Kosedag
Fig. 16 Comparison of the S%
values obtained from the
different types of water with the
distilled water
1060 I. Yilmaz, M. Marschalko
123
volume change because of swelling and shrinkage, which
causes ground movements that may damage buildings.
Swell percent and pressures of clayey soils can be obtained
from the standard laboratory experimental tests, and dis-
tilled water is generally used. However, the soil in situ
interacts with different type of waters with different
chemistries. This article particularly shows that to antici-
pate realistic soil behaviour, the water used should be the
same as that in the in situ condition that will interact with
the soil environment.
Whilst extensive studies related to the effect of the water
chemistry on the swell behaviour of clayey soils have been
published, it is very difficult to find significant literature on
effect of the test water types. As described in this article,
anticipated realistic swell percents and pressures for dif-
ferent types of natural water were lower than in the distilled
water-based experiments (Figs. 16, 17). It is clear that
anticipation of the realistic values will serve to help plan
economic projects in a way to avoid subsurface problems
and save money. It is also very important for the selection
of more economic stabilisation agents and/or expansive
soil techniques.
In order to observe changes in the swelling potential
of the soils and correlate the findings with the test water
types, the use of the same soil samples was crucial.
Therefore, bentonite samples were used in the test and
only subject to pore water chemistry changes resulting
from the different types of water samples used. In spite
of using bentonite, the results of the study presented
herein can be considered in natural (in situ) soil condi-
tions as the main aim of this article. The article will
serve to civil and geotechnical engineers, as well as
engineering seismologists, architects and urban planners
to make rational decisions in the design of new con-
struction projects.
Acknowledgments The authors thank TUBITAK for the financial
support of Project 110Y009. The authors are deeply grateful to the
anonymous reviewers for very constructive comments and sugges-
tions that led to the improvement of the quality of the paper.
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