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International Journal of Advanced Research in Engineering and Technology (IJARET) Volume 11, Issue 8, August 2020, pp. 168-183, Article ID: IJARET_11_08_017
Available online at http://www.iaeme.com/IJARET/issues.asp?JType=IJARET&VType=11&IType=8
ISSN Print: 0976-6480 and ISSN Online: 0976-6499
DOI: 10.34218/IJARET.11.8.2020.017
© IAEME Publication Scopus Indexed
STUDYING THE EFFECT OF USING CUTOFF
WALLS FOR MANAGING THE SALTWATER
INTRUSION IN HOMOGENOUS UNCONFINED
AQUIFERS: EXPERIMENTAL AND
NUMERICAL STUDY
Abdulrazak H. Almaliki
Ph.D., CE. Assistant Professor, Faculty of Engineering,
Civil Engineering Department, Taif University, Saudi Arabia
ABSTRACT
Saltwater intrusion is a global issue progressively influencing coastal aquifers,
because of climate changes and increasing ultimatum of fresh and pure water for
human consumption and irrigation. Therefore, The goal of this research was to
examine the performance of cut off walls in managing saline water intrusion and to
gain superior predictions of the saltwater wedge development and plan satisfactory
countermeasures to restrict the saltwater intrusion in homogenous coastal aquifers or
water level. This work presents a laboratory facility designed and built to simulate
saltwater intrusion in coastal aquifers, with the overall goal of providing benchmarks
for numerical models by means of different measurement techniques. Besides, the
magnitude of the solution permits us to observe the saline water wedge development
by contrasting with saltwater wedge collected at regular intervals during an
experiment in a homogeneous porous medium. The investigation comprises of two
experimental categories; the first group is for studying the saline water intrusion
without using any barriers (Base case), and the second group is for studying the effect
of substantial vertical barriers. The outcome manifest that the cutoff wall was
successful in decreasing the saltwater wedge in the examined cases with intrusion
length reduction of up to 83%.Moreover, The results showed that two zones could be
recognized; Saltwater and mixed zones. For the base case, the saltwater line and the
mixed line were high compared with the experiments used barriers. For the second
group (Vertical Solid barriers), it also noted that the saltwater and mixed lines were
decreasing by using several barriers depth. Numerical analysis showed that the cutoff
wall remained effective in repulsing the saline water wedge. The SEAWAT code
embraced to procreate the experimental outcomes. Consequently, the occurrence
between observed data and numerical simulations can give a fruitful criterion for later
researches of seawater intrusion.
Studying the Effect of Using Cutoff Walls for Managing the Saltwater Intrusion in Homogenous
Unconfined Aquifers: Experimental and Numerical Study
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Key words: Head: Seawater intrusion, cutoff wall, coastal aquifers, laboratory
experiment, numerical simulation.
Cite this Article: Abdulrazak H. Almaliki, Studying the Effect of Using Cutoff Walls
for Managing the Saltwater Intrusion in Homogenous Unconfined Aquifers:
Experimental and Numerical Study, International Journal of Advanced Research in
Engineering and Technology, 11(8), 2020, pp. 168-183.
http://www.iaeme.com/IJARET/issues.asp?JType=IJARET&VType=11&IType=8
1. INTRODUCTION
Coastal areas are the mobile region of social activities and the social economy, which is
constructed by various cities and significant activities [1, 2]. The human activities quickly
demolish the chemical and physical equality of the coastal aquifer procedure, arising in the
issues of land sinking, the water of sea intrusion , and surroundings worsening. Including, the
seawater intrusion is an issue of global tension, the over-pumping of groundwater reasons that
sea-level getting up, change of weather, and alteration of land use in the coastal region [3–5].
With these elements, groundwater pumping or driving observed to be one of the most vital
dares that encourage the severity and extent of seawater intrusion [4, 5, 6]. Consequently,
groundwater coarseness can cause by seawater intrusion or intrusion due to the utilization of
groundwater [7]. The overexploitation of groundwater has immensely intensified the expanse
of seawater intrusion in coastal regions around the globe [4, 8–10]. As it is familiar to us, the
seawater intrusion procedure is a composite issue, because the seawater intrusion is
amalgamating with fresh groundwater twosome water flow and salt transfer. It includes the
variable density groundwater flow, which is hard to reproduce well. The numerical attitudes
have immensely used to reproduce seawater intrusion in the mixing circuitry [11, 12], which
involves FEFLOW [13] and SEAWAT [9]. Werner et al. (2009) evolved a directed lab
experiment to simulate the upcoming occurrence in two proportions, with various pumping
charges and various freshwater-saltwater density[14]. Many other researchers used an
amalgamation of lab investigations and numerical representatives to study problems
associated to seawater intrusion (Chang and Clement, 2012) and (Chang and Clement, 2013)
concentrated on the influence of regenerate fluxes difference and swing of groundwater flow
and transport procedures within the saltwater wedge , in the same manner, spotlighted by
attaching colorant to the saltwater[15] ,[16]. The same method was applied by Robinson et al.
(2015) [17], who made a process for automatic image examination to change the image light
potency to consolidation, and Abdoulhalik et al. (2017) [18], in a small-scale lab investigation
to research the impact of underground barrier. A common element of the investigation above
is that they were taken out in sandboxes or flukes of reduced size, both in terms of width and
length, the first being generally less than 1 m, with a few deviations (e.g., Kuan et al., 2012)
[19], and the latter being generally less than 10 cm and even as small in size as 1 or 2 cm.
Lab investigation was examined and completed the result of cutoff walls in the unconfined
aquifer, comprising a similar situation (two cases with four physical investigations). The
SEAWAT code embraced to evaluate the stability of the experimental outcomes with the
numerical assumptions and to give a forecast on the flow instability forced in each aquifer
situation experimented. A comparative study also carried out to assess the impact of the
aquifer parameters on the overall effectiveness of cutoff walls to control sea water intrusion
(SWI).
Abdulrazak H. Almaliki
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2. MATERIALS AND METHODS
2.1. Experimental Method and Implementation
The first set represented the saltwater intrusion scenarios occurring in aquifer setting prior to
the installation of the barrier, considered as base cases. In the next set, a cutoff wall fitted into
the process. The cutoff wall created by waterproof ingredients (plasticine or clay). To make
sure that the cutoff wall pinpointed within the indigenous area of the saline water wedge for
better success [20], the cutoff wall designed on the bases of the delineation of the saline water
wedge in the homogeneous scenario (case 2-1,2-2,2-3). The cutoff wall in the second
condition of three sets was placed positioned earlier to the packing at 24.5 cm from the
saltwater tank edge with a perforation depth 35.5 cm,29.9cm and 24.7cm from the peak of the
sandbox, observing that cutoff walls are usually pinpointed within a space of double the water
level height from the coastal or close [17] [18] [19] . The success of the cutoff wall was
indicated herein means of the decrease in the percentage of the intrusion length comparative
to the base case situations R = (TL0 - TLB)/TL0, where TL0 and TLB are the intrusion length
before and after the wall equipment [21], [18].
At the beginning of each investigation, a saltwater level of 39.8 cm was compelled. In
contrast, the freshwater level was placed high enough to permit the overall porous media to
remain thoroughly saturated with fresh water. An increased amount of saltwater mixture was
continuously contributed to the saltwater pond to make sure that any possible freshwater
buoyant at the exterior was thrilled out.
Figure 1 reveals the lab tank that is 148 cm long, 10.4 cm m wide and 63cm in height,
made of Plexiglas with the heaviness of 1.5 cm. The tank comprises three bits, which are the
saline water room, moderate region, and freshwater room, along with the length indications.
The moderate region and the side room at both ends are divided by two strainer plates with
small pits. The strainer plates on either side are 30 cm away from the left saltwater edge and
the freshwater right end, in the same manner. Saltwater is drawn up with an application equal
to that of the Red Sea (average concentration of 40000 mg/L (38%)). Geotextiles laid on
either end of the strainer plates, which acts as a barrier to sand transit. The seawater region
and freshwater region are attached to the reservoirs. The two reservoirs are built of PVC
boards, with a length of 140 cm, breadth of 120cm, and a height of 60 cm, placed on the
ground. The last was colored using green food color at a concentration of 0.15 g/L to
differentiating it from the freshwater.
The investigation needed the measurements of the water level. The sea level on the left
end of the tank measured using a meter pole fastened on the iron setting. There are almost
twelve observing points of pressure measuring tubes put at the base of the back of the sand
tank to measure the level of water variance with time. To save the sand particles from getting
into the pressure measuring tubes, a filter with a mesh diameter of 0.18 mm put at the relation
between the Piezometric tube and sand tank ; the interim between all pressure vessel is 50 cm
in the parallel direction. The already used sandbox tank (size of 82L) in the investigation has
the following pits as described in Table1.
Studying the Effect of Using Cutoff Walls for Managing the Saltwater Intrusion in Homogenous
Unconfined Aquifers: Experimental and Numerical Study
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Table 1 SandBox Model description regarding the needed experiments
No Device Description
1 Freshwater Reservoir A side tank apart from the sandbox tank with a width of 10.4 cm
2 Saltwater Reservoir A side tank apart from the sandbox tank with a breadth of 10.4
cm
3 Media Sand Silicon dioxide sand (from 0.71 to 1.18 mm)
4 Water pumps One pump is utilized to feed the saltwater side tanks or tank
5 Adjustable drainage
tubes
Two tubes are used to set both freshwater and saltwater heads as
constants.
5 Drainage tube outflow Utilize to estimate or guessed the hydraulic energy and fresh or
pure water glide from the freshwater edge to the saltwater edge
6 Base tanks A 96 L located below the sandbox tank and used to supply
freshwater or saltwater.
7 Barrier Wall/
Cutoff Wall and Piles
It’s an embedded wall with a certain depth through the media
sand at a certain distance from the side tanks with a width equal
to the sandbox tank width
8 Fine mesh screens Two perforated acrylic fine mesh screens are used in both sides of
the sandbox tank as a separation between both freshwater and
saltwater tanks and the media sand
9 Barrels Barrels with known volume (10 L) are used to preparing saltwater
11 Balance For measuring the density of both saltwater and freshwater
12 Small Tank 0.5L tank for freshwater Injection
13 Injectors Injectors
14 Manometers For measuring water pressures on the bed on different locations
15 Drainage tube For drainage water from the Sandbox tank
Figure 1 Sandbox Model
Dimensionless quantities are a simple procedure in the engineering studies for decreasing
the number of investigational variables influencing a given occurrence before the
investigation; for this reason, the dimensionless quantities are used in this research, as shown
in Table 2
Table 2 Dimensionless quantities Symbols and their Definition used in this work
Symbols Definition Ratios
H Piezometric head (variable) H/SWh
Lint Intrusion Length (variable) Repulsion rate Lint/Lint
Lint Final Intrusion Length(constant)
Lmix
SWh
Mixed length (variable)
Salt Water Head (constant)
Lmix/Lfint
Xpiz Piezometric Head Distance (variable) Xpiz/Lsand
Lsand Sand Media Length (constant)
Xb Barriers Distance (parameter) Xb/Lsand
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2.2. Mathematical Model
The Mathematical representation for groundwater course or glide with variable density put in
to reproduce .The seawater intrusion procedures. Based on the licensed distinction
groundwater flow simulations represents MODFLOW, the numerical simulations model of
solute transfer in groundwater course or glide is accepted using SEAWAT, reflecting the
outcome of density on groundwater flow [22]. The program has immensely applicable in
seawater intrusion and submersible groundwater release [8]. The tow governing equations for
the groundwater flow and solute transport which are used in the SEAWAT model can be
expressed respectively as follow :
[ (
)]
[ (
)]
[ (
)]
=
( )
( ) ( )
( )
Where K f x, K f y, K f z are the hydraulic conductivities in different directions (LT-1
) ; θ
is the porosity; Sf is the specific storage (L-1
); hf is the equivalent freshwater head (L); ρ is the
density of sea or salt water (ML-3
); ρf is the density of freshwater (kg/m3); ρs is density of
water (the sources and sinks (ML-3
); qs is the volumetric flow rate of sources or sinks (T-1
); C
is the sea water concentration (ML-3
); x, y, z is the flow direction and t is the time (T). qs(T-1
)
is the volumetric flow rate per unit volume of aquifer representing sources and sinks, ν(LT-1
)
is the fluid viscosity, D(L2T-1
) is the hydrodynamic dispersion coefficient and Cs(ML-3
) is the
solute concentration of water entering from sources and sinks.
2.3. Numerical Procedure
For our purposes, we used the MODFLOW family variable, density flow rule SEAWAT. It
aided in identifying how much is investigational information or data consistent with the
numerical assumptions, offer an enhanced description of the experimental outcomes and also
realize the cut off walls’ production for multiple parameter mixture. The numerical model
made up of a rectangular domain, which measures 148 cm x 63cm constant discretized using
a size network of 0.5 cm. The longitudinal dispersivity is determined , after the trial and error
procedure, were, in the end, concluded at 0.2 cm. This result falls within the brackets of
dispersal figures described in [23]. The dispersivity and element dimensions provided
numerical stability by fulfilling the Peclet number basis [24]. Density of the freshwater and
saline water were 40000 mg/L and 0 g/L, respectively. The aquifer system was assumed to be
homogeneous. Moreover, we applied hydrostatic pressure at both the freshwater edge (C =
0%) and the coastal saline water edge (C = 38%). On the right side edge, a constant hydraulic
head of 39.8 cm for Case 1 and Case 2 set.
Additionally, the production procedures of the base case and the cutoff wall cases were
the same. To create the prediction of the cutoff wall, we rendered the cells inhabited by the
wall as inactive in the processes. In the previous scenario, the numerical model was that of a
fresh aquifer. The period for the simulation was 90 minutes, with a time step of the 20s. For
each time step, the hydraulic heads on the seafloor revised according to equation (1). At first,
in case 1, the transient simulations was used to determine the extent of saline water intrusion
without setting the cut off the wall in the aquifer. Whereas, in case 2, the transient production
Studying the Effect of Using Cutoff Walls for Managing the Saltwater Intrusion in Homogenous
Unconfined Aquifers: Experimental and Numerical Study
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used to identify the expansion of saline water intrusion under the scenario of the prevalent cut
off wall at space 24.5cm. It did not include the consideration of pumping in the aquifer.
3. RESULT AND DISCUSSION
Two group of experiments conducted to research the use of cut off wall effects on saltwater
intrusion and new groundwater level variation in the coastal unconfined aquifers. During both
group of experiments, the change of the port between water of the sea and freshwater and the
dissimilarity of the level of groundwater at each observing point considered until the process
reached the final stable state. In this region, we concentrate on the outcomes of both scenarios
with their discussion
In the base case, the saltwater line progresses less than the mixed line during the same
period determined for the experiment. Figure 2 illustrates the relation between the salt line
and mixed Line progress in time. The mixed line continues to advance until the end of the
experiment. This experiment conducted without using the barrier to see the natural progress of
saltwater to be the benchmark and reference in future experiments. Figure 3 shows the
transient hydraulic head variation along with the sandbox model. Moreover, Figure 4 shows
sample photos of the progress of both saltwater and mixed lines.
Figure 2 Progress of salt and mixed lines achieving Distance along with sandbox model (Base Case)
Figure 3 Relation between Piezometric Head and steady-state after 90 minutes (Base Case)
0
1
2
3
0 50
Lin
t/L
fin
t
Time (min)
M…S… 0.00
0.100.200.300.400.500.600.700.800.901.001.101.20
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
H/S
Wh
Xpiz/Lsand
T=0min T=5minT=10min T=15min
0
0.5
1
1.5
2
2.5
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Lm
ix/L
fin
t
Lint/Lfint
0
10
20
30
40
50
0 50 100
Intr
usi
on
len
gth
in
cm
Time
Abdulrazak H. Almaliki
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Figure 4 Photos showing the progress of saltwater and mixed lines with time (Base Case)
Figures 5, 7 and 9 present the variation of intrusion length, saltwater repulsion rates
(Lint/Lfint) of intrusion line, mixing line and simulated of the salt wedge with time in the
unconfined aquifer. It represents that the numerical model assumed correctly the intrusion
length and repulsion rate of the saltwater wedge considered in the real picture. As same to
Figures 5(b), 7(b) and 9(b) show that the intrusion length enlarging with time the start and
then tends to be a stable value under the requirement of using cut off the wall after 90 min. of
simulation. The final intrusion length of the steady-state for the base case without using cut
off the wall was 49cm. While The final intrusion lengths of the steady-state with using cut off
a wall at a distance of 24.5 cm from the seawater tank are 41,40.6 and 40.1 cm for case 2-1,2-
2 and 2-3, respectively. Then, the intrusion length enlarges with time when the cut off wall
placed higher than the bed, but it is still low.
When the depth of cut off wall decreased to 24.7, the seawater besides encroaches toward
freshwater until a new steady condition reached. The saltwater intrusion length enlarges with
time a bit until it is stable (Figure 9(a)). The saltwater repulsion rate Lint/Lfint enlarged with
time and extended the highest value at the time of 90 min (Figures 5(b), 7(b) and 9(b) ). It
designates that the stable-state of the seawater encroachment can conclude according to the
saltwater repulsion rate Lint/Lfin of seawater intrusion length. The maximum values of
saltwater intrusion length were 49cm without using cut off wall and 41 cm using cut off the
wall (Figures 5(b), 7(b) and 9(b)). The saltwater intrusion length with using cut off wall for
case 2-1 is larger than that of the case 2-3 because the depth of the cut off wall is higher than
that of the case 2-3. Therefore, as cut off wall penetrate more profound as the saltwater
intrusion decreases. Figures 5(C), 7(C), and 9(C) show the transient hydraulic head variation
along with the sandbox model. It indicates that the ground freshwater level increases with the
existence of a cut off wall.
Studying the Effect of Using Cutoff Walls for Managing the Saltwater Intrusion in Homogenous
Unconfined Aquifers: Experimental and Numerical Study
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Figure 5(a) Progress of salt and mixed lines achieving steady state after 90 minutes (Case 2-1)
Figure 5(b) Comparison between experimental and numerical intrusion length data in cutoff wall (case 2-1).
Figure 5(c) Relation between Piezometric Head and Distance along sand box model (Case 2-1)
0.80
0.90
1.00
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
H/S
Wh
Xpiz/Lsand
T=0min T=5min T=10min T=15min T=20min
T=25min T=30min T=35min T=40min T=45min
T=50min T=55min T=60min T=65min T=70min
T=75min T=80min T=85min T=90min
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
0 20 40 60 80
Lin
t/Lf
int
Time (min)
Mixed Line Salt Line
Simulated
15
20
25
30
35
40
45
0 20 40 60 80 100
intr
usi
on
len
gth
(cm
)
Time (min)
Salt Line Intrusion
simulated
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Figure 5(d) Relation between Mixed Length and Intrusion Length (Case 2-1)
Figure 6 Photos showing the progress of saltwater and mixed lines with time (Case 2-1)
Regarding case2 (using vertical barriers), from Figure 5(a), Figure 7(a) and Figure 9(a), it
could be shown that the ratio Lint/Lfint is slightly increase with time until became a constant
value of 0.9 at 90 minutes. Moreover, from the same Figures, it could be shown that the
mixed zone is continually enlarged with time. As shown in Figure 5(c), Figure 7(c) and
Figure 9(c), The initial head difference between freshwater and saltwater side tanks fixed to
be 10cm. After running the experiment, the Piezometric heads increased with time until
reaching the same saltwater level. Figures 5(d), Figure 7(d) and Figure 9(d) show the relation
between the saltwater repulsion Lint/Lfint and mixed water intrusion Lmix/Lfint. For the
mixed line length represented by the ratio Lmix/Lfint, Figure 5(d), Figure 7(d) and Figure
9(d) illustrates that this ration is continued increasing with increasing the saltwater repulsion
(Lint/Lfint).
Figure 5(a), Figure 7(a) and Figure 9(a) show the observed values and measured values of
the seawater repulsion rate with using cut off wall at a distance 24.5 from the saltwater tank
with three deferent depths 35.5 cm,29.9 cm and 24.7 cm for Case 2-1,2-2,2-3 respectively.
The match between the observed and calculated saltwater intrusion is well, as shown in Figure
5(b), Figure 7(b) and Figure 9(b). As the cut off wall rises from the low depth (24.7 cm) to
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Lm
ix/L
fin
t
Lint/Lfint
Studying the Effect of Using Cutoff Walls for Managing the Saltwater Intrusion in Homogenous
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high depth (35.5 cm), the intrusion decreases under the effect of using cut off wall depth
(green lines of Figures 5(a)–9(a)) with an improvement of 83%.
Figure 7(a) Progress of salt and mixed lines achieving steady state after 90 minutes (Case 2-2)
Figure 7(b) Comparison between experimental and numerical intrusion length data in cutoff wall (Case 2-2)
Figure 7(c): Relation between Piezometric Head and Distance along sand box model (Case 2-2)
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 10 20 30 40 50 60 70 80 90
Lin
t/L
fin
t
Time (min)
Mixed line
Salt Line
Simulated
15
20
25
30
35
40
45
0 20 40 60 80 100
Intr
usi
on
len
gth
cm
Time (min)
Salt Line Intrusion
Simulated
0.80
0.90
1.00
1.10
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
H/S
Wh
Xpiz/Lsand
T=0min T=5min T=10min T=15min T=20minT=25min T=30min T=35min T=40min T=45minT=50min T=55min T=60min T=65min T=70minT=75min T=80min T=85min T=90min
Abdulrazak H. Almaliki
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Figure 7(d) Relation between Mixed Length and Intrusion Length (Case 2-2).
Figure 8 Photos showing the progress of saltwater and mixed lines with time (Case 2-2)
Figure 5(c), 7(c) and 9(c) show the observed values of the groundwater level with using
cut off wall at a distance 24.5 from the saltwater tank with three deferent depths 35.5 cm,29.9
cm and 24.7 cm for Case 2-1,2-2 and 2-3 respectively. As the cut off wall rises from the low
depth (24.7 cm) to high depth (35.5 cm), the fresh groundwater level increases under the
effect of using cut off wall depth. Figure 6, Figure 8 and Figure 10 show sample photos of the
progress of both saltwater and mixed lines in case 2-1,2-2 and 2-3, respectively.
Figure 9(a) Progress of salt and mixed lines achieving steady state after 90 minutes (Case 2-3)
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 1 2
Lm
ix/L
fin
t
Lint/Lfint
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
0 20 40 60 80
Lin
t/L
fin
t
Time (min)
Mixed Line
Salt Line
Simulated
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Figure 9(b) Comparison between experimental and numerical intrusion length data in cutoff wall
(Case 2-3)
Figure 9 (c) Relation between Piezometric Head and Distance along sand box model (Case 2-3
Figure 9(d) Relation between Mixed Length and Intrusion Length (Case 2-3).
15
20
25
30
35
40
45
0 20 40 60 80 100
Intr
usi
on
len
gth
in c
m
Time (min)
Salt Line Intrusion Simulated
0.80
0.90
1.00
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
H/S
Wh
Xpiz/Lsand
T=0min T=5min T=10min T=15minT=20min T=25min T=30min T=35minT=40min T=45min T=50min T=55min
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Lm
ix/L
fin
t
Lint/Lfint
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Figure 10 Photos showing the progress of salt water and mixed lines with time (Case 2-3)
Figure 11 (a) Comparison between experimental mixing zone length data in the base and cutoff wall
cases
From figures 11(a) and (b), it was noted that the saltwater line and the mixed line were
high in the base case, and it was also noted that the saltwater line was decreasing due to the
existence of the barrier. On the other hand, the saltwater progresses decreases with decreasing
the depth of the barrier. It may be because of the vertical currents formed below the barrier
depth. Moreover, with decreasing the depth of barrier, both salt and mixed lines are close in
results to the base case. The intruding migration rate in Case 2-1 was relatively more
significant than that in Case 2-2 and Case2-3. It means that faster seaward motion of the
seawater wedge would occur when the depth of cut off wall is small in the coastal aquifers.
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
2.00
0 10 20 30 40 50 60 70 80 90
Lm
ix/L
fin
t
Time (min)
Case1 ( Base case )
Case2-1(Vertical Barriers)
Case 2-2 ( Vertical Barriers)
Case 2-3 ( Vertical Barriers )
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Figure 11 (b) Comparison between experimental sallt water intrusion length facts in the bottom and
cutoff wall cases
4. CONCLUSIONS
In this study, we have utilized lab experiments and numerical simulations to examined the
successfulness of cutoff walls in homogenous coastal aquifers. Four manifold scenarios were
examined, including a base case and cases with cut off at deferent depth 35.5,29.9 and 24.7
cm at a distance 24.5cm from the saltwater tank. The intrusion length data were investigated
by examining every experimental run. The SEAWAT model sensibly well assumed the
experimental repulsion and saltwater intrusion length in the four situations. The matches
between the measured and calculated repulsion and saltwater intrusion length outcome of the
three experimented scenarios are well. The simulations outcome for the cutoff wall
investigation yielded a good occurrence with the investigational data. The numerical model
established that the cutoff wall was successful in keeping the saline water on the coastal side
of the wall for all the head dissimilarities trialed out and in all the experimented arrangements,
in occurrence with the experimental observations. In the base case, the saltwater line
progresses less than the mixed line during the same period determined for the experiment. In
case 2-1, the barrier at a depth of (35cm), and note that the progress of saltwater and mixed in
saturated soil is less than the base case. For other cases (case 2-2 and 2-3), it noted that the
saltwater and the mixed lines decreased progressively from the last experiments and became
close relatively to the base case results in the last case (Case 2-3). Conclusively, with
decreasing the barrier depth, both the saltwater line and the mixed line were decreasing
toward the base case results, and the best results were found for the case 2-3. The outcomes
from this study will aid in future planning, design considerations and management of artificial
recharge well facilities to reduce and control seawater intrusion in unconfined coastal
aquifers.
ACKNOWLEDGEMENT
I thank my colleague in the water resources group in Taif university Dr. Wael Elham for
implementing the experiments and offering me the data for analyzing and finishing this
research.
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Time (min)
Case1 ( Base case )Case2-1(Vertical Barriers)Case 2-2 ( Vertical Barriers)Case 2-3 ( Vertical Barriers )
Abdulrazak H. Almaliki
http://www.iaeme.com/IJARET/index.asp 182 editor@iaeme.com
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