4. INTRODUCTION
Expansion of clays is caused due to wetting of soil,which
results in volume increase.
It causes serious damage to civil engineering structures.
Cyclic expansion and shrinkage of clays and the
associated movements of foundations may result in
cracking and fatigue to structures.
By cyclic swelling it is meant that a soil specimen is
wetted and allowed to swell then dried to its initial water
content at room temperature , then wetted again to
swell, dried once more, and so on.
5. SCOPE OF PRESENTATION
The basic objective of this study was to investigate
the effect of cyclic swelling on the expansive
characteristics of clays.
When clay specimens are repeatedly subjected to
full swell than allowed to desiccate to their initial
water content show sign of fatigue after each cycle
,thus exhibiting less expansion.
The swelling potential increases with the number of
wetting and drying cycles.
Expansion reaches an equilibrium state after about
3 to 5 cycles.
8. CASE STUDY
Project : Cyclic Swelling Behavior of
Clays.
Location : Irbid a city in Northern
Jordan.
Objective: Determining swell-shrink
behavior of clay.
9. PROJECT BACKGROUND
To study the effect of cyclic swelling on the
expansive characteristics of clays six expansive
soils were obtained from various locations in Irbid
(a city in northern Jordan).
Previous investigations of Irbid soil (Masoud 1988)
indicated that it consists of
Properties Percentage
Clay 50-80
Silt 10-45
Sand 2-15
Liquid limit 65-90
Plastic limit 15-40
Shrinkage limit 10-20
10. All of these properties. along with Irbid city being in
a semiarid region. serve only to indicate that the
soil in this area is expansive in nature.
Additionally, clays in this area are generally
classified as highly to very highly expansive in
nature (Basma 1993).
To accomplish the desired objectives and as was
stated earlier, six soils from various locations were
utilized in this study.
11. PROPERTIES OF TEST SOILS
Propert
y
A B C D E F
Depth of
sampling
(m)
4.0 6.0 6.0 3.5 3.0 2.5
Initial
water
content,
W(%)
12.0 21.0 20.3 20.0 15.0 20.0
Initial dry
unit
weight
(kN/m')
16.0 l7.0 16.0 l7.0 16.8 17.2
LL 35 79 57 75 62 81
PI 22 27 15 37 34 38
12. Propert
y
A B C D E F
Grain
size
distributi
on
Sand
(%)
32.0 8.0 38.0 3.0 20.0 5.0
Silt (%) 32.1 33.2 29.8 20.0 28.9 23.3
Clay (%) 37.9 58.8 32.2 77.0 51.1 71.7
13. TESTING PROCEDURE
Remoulded specimens were prepared by
compacting the soil at its natural water content and
dry unit weight directly into the consolidation ring.
The compacted soil sample was placed in a
consolidation cell between air-dry porous stones and
subjected to a vertical confining pressure of 6.9 kPa
(I psi).
It should be noted that for each soil considered, two
identical samples were prepared, as was just
mentioned. The first specimen was used to
determine the swell percent and the second was
utilized to assess the swell pressure.
14. To determine the percent swell the sample was
inundated with distilled water. allowing it to fully swell
for at least 40 hr.
At this stage, the water was removed and the
consolidation cell was dismantled.
The test sample (still within the consolidation ring) was
then allowed to air-dry to its initial water content within
the laboratory environment.
Measurements of water loss for each sample were
recorded at intervals of approximately 15 min for the
first 3 hr, then every 100 min thereafter to 500 min,
then at I day.
15.
16. Cycles after at least 48 hr of wetting followed by the air
drying period required to revert the samples to their
initial water contents were repeated for the six soils.
For brevity and space limitation, a plot of the vertical
swell and shrinkage for only two soils, namely, A and
F, as function of time are presented below.
17.
18.
19. The change in swell pressure with the number of
wetting and drying cycles was also determined by the
constant volume swell test.
In this test. the samples were air dried to their
corresponding initial water contents then fully
inundated with distilled water.
As swelling commences, vertical deformation was
prevented and the samples were kept at their initial
void ratio by continuously adding loads at every
vertical expansion.
The loads were continually added until no expansion
was observed.
At this stage the swell pressure was calculated as the
load required to retain zero swell divided by the
specimen area.
20. CHANGE OF SWELL POTENTIAL AND SWELL PRESSURE
WITH CYCLE
NUMBER FOR TEST SOILS
21.
22. SUMMARY AND CONCLUSION
Swelling and swell pressure decrease with
increasing number of cycles.
The most reduction in swelling and swell pressure
was recorded after the first cycle.
Even though both properties decrease, they seem to
level off after about 4 to 5 cycles.
23. REFERENCES
Effect of Micro fabric on Undrained Static and
Cyclic Behavior of Kaolin Clay.
Cyclic Triaxial Tests on remoulded clays.
Rate effects and cyclic loading of sensitive clays.
