Effect of wetting-Drying cycles on surface cracking and swell-shrink behavior of expansive soil modified with ionic soil stabilizer

 Journal of Mining and Earth Sciences Vol. 61, Issue 6 (2020) 1 - 13 1 
Effect of wetting-drying cycles on surface cracking 
and swell-shrink behavior of expansive soil modified 
with ionic soil stabilizer 
Huan Minh Dao *, Anh Thuc Thi Nguyen, Tuan Manh Do 
Faculty of Geology, Hanoi University of Natural Resources and Environment, Hanoi, Vietnam 
ARTICLE INFO 
ABSTRACT 
Article history: 
Received 21st Sept. 2020 
Accepted 23rd Nov. 2020 
Available online 31st Dec. 2020 
 This paper presents the results of an experimental investigation of the 
effect of wetting-drying cycles on the surface cracking and swell-shrink 
behavior of modified expansive soils. An image processing technique was 
employed to understand this effect by quantifying the surface crack area 
density, crack number, crack length, mean crack width, and absolute 
shrinkage. Parameters such as height, the relative rate of expansion, and 
linear shrinkage were used to characterize the effect of wetting-drying 
cycles on the swell-shrink behavior of the specimens subjected to various 
overburden pressures. The results showed that the increase in the number 
of wetting/drying cycles accelerated the crack growth and led to the 
increased crack number, total crack length, and surface crack area 
density. Moreover, as the number of wetting/drying cycles increased, the 
absolute shrinkage to be on the rise, and the mean crack width exhibited 
fluctuation characteristics. Furthermore, the moisture content was 
inversely related to the crack extent. For the specimens subjected to 
various overburden pressures, the height and the moisture content 
showed a good linear relationship. With the increase in wetting/drying 
cycles, the relative rate of expansion of the specimen decreased. 
Additionally, a larger overburden pressure resulted in a lower relative 
rate of expansion; however, as the number of wetting/drying cycles 
increased, the relative rate of linear shrinkage increased and then 
decreased. 
Copyright © 2020 Hanoi University of Mining and Geology. All rights reserved. 
Keywords: 
Crack, 
Swell-shrink behavior, 
Treated expansive soil, 
Wetting-drying cycles. 
1. Introduction 
Expansive soil is a naturally occurring ground 
that can interact with water and therefore changes 
in volume and structure occur (Сорочан, 1982). It 
is mainly constituted of strongly hydrophilic clay 
minerals such as montmorillonite (smectite),
_____________________ 
*Corresponding author 
E-mail: dmhuan@hunre.edu.vn 
DOI: 10.46326/JMES.2020.61(6).01 
2 Huan Minh Dao and et al./Journal of Mining and Earth Sciences 61 (6), 1 - 13 
illite, palygorskite, and kaolinite (Al-Rawas and 
Goosen, 2006). The presence of montmorillonite 
clay in these soils imparts its high swell-shrink 
potentials (Chen, 2006). Therefore, it is a kind of 
soil that expands and softens when water is 
absorbed whereas it shrinks and cracks when 
water dries out. Due to these characteristics, 
expansive soils have worldwide problems 
(Erguler and Ulusay, 2003). For example, the 
estimated damage to buildings, roads, and other 
structures built on expansive soils exceeds 15 
billion dollars in the Usannually (Al-Rawas and 
Goosen, 2006). Such soils are considered natural 
hazards that pose challenges to civil engineers, 
construction firms, and enterprise owners. 
Principally, swelling occurs when water infiltrates 
between the clay particles, causing them to 
separate. Researchers have made several 
attempts to obtain the swelling or shrinkage 
characteristics of the expansive soils. Some 
progress has been made toward characterizing 
the swelling and shrinkage characteristics, 
despite the complexity of behavior (Boivin et al., 
2006; Cornelis et al., 2006; Rao et al., 2004; Nayak 
and Christensen, 1971). 
Some scholars also conducted studies on the 
effect of moisture on surface cracking. Lu et al. 
(2002) investigated the crack evolution of 
Nanyang remolded expansive soil during wetting-
drying cycles using computerized tomography 
(CT). From the CT data, they defined a crack 
damage variable and analyzed its relationship 
with the soil‘s accumulative drying volume. Yuan 
and Yin (2004) proposed the gray level entropy as 
an index to measure and evaluate the 
development extent of the cracks in the expansive 
soils. Tang et al. (2007) employed an image 
processing technique to quantitatively analyze 
and describe the structural and geometric 
characteristics of cracks in clay during the process 
of drying and shrinkage. Li et al. (2009) used the 
image processing technique to analyze the 
relationship between the cracks' fractal 
dimension in the expansive soils and the crack 
density. Zeng et al. (2013) utilized mercury 
intrusion porosimetry (MIP) to study the changes 
of the pore in expansive soil during wetting-
drying cycles. The results showed that the 
microstructural parameters of expansive soil 
increased with the rising number of 
wetting/drying cycles, such as the total volume of 
the pores, the porosity, and the average pore 
diameter. Zhang et al. (2011) carried out 
laboratory wetting-drying tests on Nanyang 
expansive soil to investigate the crack evolution 
characteristics. The vector diagram technology 
was employed to characterize the crack photos to 
extract its geometric features. The effect of 
structural damage on yielding characteristics of 
the expansive soils investigated the 
microstructure changes of the soil immersed in 
water and subject to wetting-drying (Yao Zhihua 
et al., 2010; Yao Zhihua et al., 2010). Tang et al. 
(2012) established a sound theory for 
characterizing desiccation cracking in a study on 
desiccation cracking behavior of expansive soil. . 
Yang et al. (2006) carried out an experimental 
study to reveal the effect of wetting-drying cycles 
on the expansive soil's strength and deformation 
characteristics under ... men showed 
an excellent linear relationship with the moisture 
content. Moreover, when the overburden 
pressure was 0 kPa, the relationship between the 
specimen's height and the moisture content 
presented some linear characteristics initially; 
however, as the moisture content decreased, 
some irreversible deformation occurred. For the 
expansive soil subject to various overburden 
pressures, its swell-shrink deformation is 
controlled mainly by the moisture content and the 
external force acting on it (Zhan, 2007). It 
indicated that the overburden pressure inhibited 
the swelling or expansion induced by water 
adsorption. 
The mechanism underlying the above 
changing characteristics is given below. The 
existing theories, such as the electric double layer 
theory, concluded that the main reason for the 
expansion of the expansive soil after water 
absorption was due to the increase in the 
thickness of the water film between the soil’s 
crystal layers or particles (Bowers et al., 2018). As 
shown in Figure 1, the ideal non-contact spherical 
particle model, the water film distribution 
showed zoning characteristics. During the water 
loss/drying process, water contained in the space 
between the aggregates was the one that 
dissipated the first due to the attraction between 
the polar molecules or ions and the Van der Waals’ 
force between the molecules. The dissipation of 
the water in the space resulted in a decrease in the 
thickness of the water film between the crystal 
layers. Its microscopic manifestation was due to 
the shrinkage of the expansive soil. After the 
water's dissipation, the ideal non-contact 
spherical particle model was reduced to an ideal 
contact spherical particle model. Then the bound 
water formed due to hydration began to dissipate. 
However, as there was no space between the 
aggregates, the bound water's dissipation did not 
cause the expansive soil's shrinkage anymore. It 
was consistent with the shrinkage experimental 
results: the expansive soil's shrinkage limit was 
the maximum shrinkage extent of the expansive 
soil when it dried. 
Figures 9 and 10 show the changes in the 
relative rate of expansion and the relative rate of 
linear shrinkage against the number of the 
wetting-drying cycle as the specimen is subjected 
to various overburden pressures. Figures show 
that as the number of the wetting-drying process 
increased, the relative rate of expansion of the 
specimen under various overburden pressures all 
decreased gradually. The greater the overburden 
pressure, the smaller the relative rate of 
expansion, indicating that the overburden 
pressure inhibited the swelling or development 
induced by water adsorption. For the modified 
expansive soil that is not fully saturated, a smaller 
external force can have a more significant effect 
on its swelling characteristics. As the number of 
the wetting - drying cycle increased, the relative 
rate of linear shrinkage of the specimen under 
various overburden pressures all increased first 
and then decreased; the relative rate of linear 
shrinkage reached the peak value during the 
second wetting-drying cycle. The microscopic 
particle of the expansive soil aggregated into 
various parts, leaving pores in between. The 
pores’ characteristic is one of the main factors
Figure 8. Changes in the specimen's height against 
the moisture content under various overburden 
pressures during the second wetting-drying cycle. 
 Huan Minh Dao and et al./Journal of Mining and Earth Sciences 61 (6), 1 - 13 11 
that determine how the expansive soil behaves 
during shrinking and swelling (Hai-bo et al., 
2009). As the soil absorbs water the first time, it 
expands, and the pores between the aggregates 
are filled by water. In the meantime, water film 
increases in thickness, resulting in the further 
swelling/expansion of the soil. Also, changes take 
place in the structural form between the 
aggregates. The aggregates can expand and 
undergo self-rotation due to the unbalanced force 
induced by water adsorption. As a result, the pore 
ratio of the expansive soil grows. During the water 
loss (drying) process, the free water contained in 
the space between the aggregates is the one that 
dissipates first, while in the meantime, tensile 
cracks begin to develop inside the soil. In the first 
wetting-drying cycle, the generated tensile cracks 
did not play a prominent role in swell-shrink 
deformation (Tang et al., 2016). However, a 
significant role was played in the second wetting-
drying cycle as the generated tensile cracks 
coalesce and grow, destroying the soil’s integral 
structure, causing a significant number of micro-
cracks inside the aggregates. As a result, the 
strength of the soil decreases materially. This is 
further compounded by the overburden pressure, 
which results in the collapse of the aggregates. 
Therefore, in the second wetting-drying cycle, the 
swell-shrink deformation also involves the 
deformation induced by the aggregates' collapse. 
It explains the relative rate of linear shrinkage 
reaches the peak value in the second wetting-
drying cycle, and it reduces as the number of the 
wetting-drying cycle increases. 
5. Conclusions 
(1) The number of wetting-drying cycles 
affects the development of cracks in the modified 
expansive soil. As the number of the wetting-
drying cycle increases, cracks develop profusely. 
In comparison with the second wetting-drying 
cycle, in the third wetting-drying cycle, the surface 
crack area density increases by 1%, the crack 
number grows by 99%, the total crack length 
increases by 85%, the absolute shrinkage grows 
by 85%, and the mean crack width expands by 
83%. 
(2) During the drying of the modified 
expansive soil, the moisture content, in general, is 
inversely related to the crack extent. As the 
moisture content decreases, parameters like 
surface crack area density, crack number, total 
crack length, and absolute shrinkage increasing 
by 8%, 11%, 5%, and 30%, respectively, at each 
moisture content recoding point. However, the 
mean crack width, it changes irregularly as the 
overall swell-shrink of the specimen causes 
significant changes in the crack width. 
(3) The modified expansive soil is over-
consolidated and shows significant swell-shrink 
characteristics in the wetting-drying cycle. Cracks 
are easy to develop in the modified expansive soil. 
Also, it is a collapsible soil. Under high moisture 
Figure 9. Changes in the relative rate of expansion 
against the number of the wetting-drying cycle as 
the specimen being subject to various overburden 
pressures. 
Figure 10. Changes in the relative rate of linear 
shrinkage against the number of the wetting-
drying cycle as the specimen being subject to 
various overburden pressures. 
12 Huan Minh Dao and et al./Journal of Mining and Earth Sciences 61 (6), 1 - 13 
content, under the overburden pressure, crack in 
the expansive soil closes and the soil undergoes 
significant restructuring. As the number of the 
wetting-drying cycle increases, the height of the 
specimen decreases. In comparison with the 5% 
moisture content recording point at various 
overburden pressures, the specimen’s height on 
average increases by about 1 mm at the 35% 
moisture content recording point. 
(4) The overburden pressure has an 
inhibition effect on the modified expansive soil's 
swell-shrink characteristics. As the number of the 
wetting-drying cycle increases, more and more 
cracks develop in the expansive soil, which is 
accompanied by the occurrence of apparent 
macroscopic cracks and plane of failure and the 
material increase of the pore ratio. Compared 
with the first wetting-drying cycle, the relative 
rate of expansion in the third wetting-drying cycle 
reduces by 41%. The repeated wetting-drying 
cycle has destroyed the specimen's internal 
structure, causing many cracks. When the 
moisture content reaches a certain level, and the 
overburden pressure is significant enough, the 
expansive soil would also undergo collapsible 
deformation after repeated wetting-drying. 
Acknowledgment 
This research did not receive any specific 
grant from funding agencies in the public, 
commercial, or not for profit sectors. 
The author would like many thanks to Dr. 
Nguyen Thi Thuc Anh and Do Manh Tuan for 
English editing and comments. All these 
contributions have helped a lot to improve the 
quality of the paper. 
Conflict of interest 
All authors declare no conflict of interest. 
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