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)


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


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


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-)


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


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 %


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




samples collected from gypsum

rock


123



from the swell tests using the

water samples collected from

lake




samples collected from Tecer


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




samples collected from Kosedag

Fig. 16 Comparison of the S%

values obtained from the

different types of water with the

distilled water


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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