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8/3/2019 Physical Modelling Projects in Mhi
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LIST OF PHY
HYDRAU
National Hydraulic
Ministry of
ICAL MODELLING PROJE
IC AND INSTRUMENTATI
LABORATORY
Research Institute of Malaysia (NAHRI
Natural Resources & Environment (NRE
www.nahrim.gov.my
TS IN
ON
))
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LIST OF PYSICAL MODELLING PROJECTS IN HYDRAULIC AND
INSTRUMENTATION LABORATORY
NO. PHYSICAL MODELLING CLIENTCOST
(RM) DATE
1.
STUDY ON SUITABILITY OF GEO TUBE TO
ADDRESS EROSION PROBLEM FOR
MANGROVE REPLANTING AT SG.HJ.
DORANI, SELANGOR DARUL EHSAN
FRIM 200,000 MAY 2010
2.
HYDRAULIC MODEL INVESTIGATION OF
THE PROPOSED ALTERATION OF BATU DAM
SPILLWAY, SELANGOR DARUL EHSAN
PUNCAK
NIAGA SDN
BHD
150,000 APRIL 2007
3.
STRUCTURAL STABILITY OF ROCK
ARMOUR AS GROYNE FOR BATU MANIKAR
BEACHES, FEDERAL TERITORY OF LABUAN
PERBADANAN
LABUAN50,000 JUNE 2010
4.
FLOOD MEDELLING EVALUATION IN RIVER
MEANDERING CHANNEL UNDER TIDAL
EFFECT FOR SUNGAI SELANGOR
IN HOUSE 100,000 JULY 2008
5.
STRUCTURE STABILLITY TESTING FOR
ARMOUR ROCK REVETMENT DESIGN AT
TANJUNG PIAI, JOHOR DARUL TAZIM
IN HOUSE 20,000MARCH
2010
6.
STUDY OF WABCORE ARTIFICIAL REEF
STABILITY FOR BREAKWATERIN HOUSE 50,000
AUGUST
2010
7.THE DEVELOPMENT OG H-BLOCK FORRIVER BANK PROTECTION
IN HOUSE 30,000 JANUARY2010
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PHYSICAL MODELING 1: STUDY ON SUITABILITY OF GEO-TUBE TO ADDRESS
EROSION PROBLEM FOR MANGROVE REPLANTING AT SG. HJ. DORANI
1. Background
Sg. Hj. Dorani (Figure 1) which is located near Sabak Bernam area is one of the selected location for
mangrove replanting program after the December 2004 Tsunami event in Malaysia. To increase the
potential of survival rate of replanted mangrove, Department of Irrigation and Drainage (DID) has
installed a geo-tube in front of the replanting area to break the incoming wave before it hit the coastal
shoreline and the mangrove replanting area. Physical modeling was proposed to evaluate the potential
deposition of sedimentation at the site. In addition, physical model served as a tool to evaluate complex
coastal phenomenon that are not sufficiently address by numerical models.
Figure 1: Study Area
Sg. Hj. Dorani coastline area is very diverse and exposed to prominent coastal physical parameter such as
tide, wave and current impact, and is dominantly influenced by tidal fluctuation. In house marine data
collection exercise by NAHRIM revealed that the bathymetry condition at the study area is quite gentle.
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Following this, NAHRIM has developed a physical model to provide better understanding of the coastline
responds due to wave action. A cohesive bed model was constructed at NAHRIMs Hydraulic and
Instrumentation Laboratory using 2D wave basin with a scale of 1: 20.
2. Objectives
The main objective of the study can be described as follows:
i. To evaluate the possible cause of ongoing erosion problem at Sg. Hj. Dorani shoreline.ii. To analyze the sedimentation pattern at existing Geo-tube installation area and the erosion rate at
Sungai Haji Dorani shoreline.
iii. To propose suitable counter measure for the positioning of geo-tube for mangrove replanting.
3. Methodology
Sungai Hj Dorani model was constructed with the size of 26 m x 24 m, which represent an area of 350 mx 520 m on site, as shown in Figure 2 below.
Figure 2: Model Design for Physical Test
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The work flow of the physical model is as shown in Figure 3.
Figure 3: Sungai Hj Dorani physical modeling work flow
Model Scaling
Model Construction
Instrument Calibration
First option testing (144 hours)
Measurement & Analysis
Model Reconstruct
Second option testing (144 hours)
Measurement & Analysis
Result comparison
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Table 1 below shows the calculated scaled parameters that were tested for the particular model.
Table 1: Sg. Hj. Dorani Scaled Parameter
The test was carried out for 144 hours, which is equivalent to 32 days in nature. Bed level profile wasmeasured after 72 hours. Bed profile changes showed some significant sediment movement pattern along
the test period.
4. Results
Sungai Hj Dorani coastline bathymetry area was measured to be less than 1 meter during the low tide
condition. The coastal water is withdrawn from near shore area about 2 km and the geo-tube area wasexposed throughout that period (Figure 3). Waves that present at Sg. Hj. Dorani area was also one of the
major factor that contributes to erosion and deposition surrounding the geo-tube area. Sungai Hj Dorani
coastline is also facing occurrence of breaking type of wave due to gentle water depth changes at the
study area.
When the depth of water is less than half the wavelength, waves begin to interact with the bottom area
and become shallow water waves. As the depth decreases the waves slow up and steepen. At water depth
SG. HJ. DORANI. PHYSICAL MODEL
Geometric Scale, Lr 20
Then Velocity scale and Time scale 4.5
Parameter Prototype Model Scale
Breakwater Length, (m) 200.00 10.0
Breakwater Height, (m) 4.50 0.225
Breakwater Width, (m) 3.50 0.175
Average Current Velocity (m/s) 0.15 0.034
Design Wave Height, Hda (m) 0.36 0.018
Design Wave Height, Hmax (m) 0.57 0.0285
Wave Period (s)m, ave of Ave (3-5) 4.60 1.2
Tidal Range Max (m) 4.20 0.21
Tidal Range Min (m) 1.50 0.075
Tidal Range Ave (m) 2.30 0.115
Tidal Range (m), Design 2.30 0.115
Beach Material size (Silt)(mm) 0.05 0.0025Falling Velocity ( cm/s) 0.72 0.036
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of 1.3 times the wave height is reduced and the particles of water in the crest have no room to completetheir cycles. At this point the wave breaks, and moves out of the wave generation area so that the wave
period is conserved. This is an important observation since it enables us to predict when waves will begin
to act as shallow-water waves.
This phenomenon induces wave refraction at the geo-tube area and straight to the shoreline. The current
wave condition in the deeper water area caused critical erosion at southern part of the geo-tube area.
Figure 3: Condition in basin after the first Test
Figure 4: Erosion and Deposition of Model Area
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5. Conclusion
Counter measures needs to be taken to minimize the erosion factor. As best solution option, the geo-tube
was suggested to be placed at distance of 120m 150m from the shoreline area. This will allow the
incoming waves to be refracted with allowable space before they hit the coastline. This option also
increases level of sedimentation behind the geo- tube area, thus provide buffer area to protect themangrove replanting site.
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PHYSICAL MODELING 2: HYDRAULIC MODEL INVESTIGATIONS OF THE
PROPOSED ALTERATION OF BATU DAM SPILLWAY, SELANGOR DARUL EHSAN
1. Background
NAHRIM have carried out a physical modelling for study the efficiency of the new proposed
spillway at Batu Dam. This is part of the Scheme No. 3: Transfer of Raw Water from Batu Pondand Pumped Storage at Batu Dam which is proposed to mitigate expected water deficit in
Selangor and Kuala Lumpur.
Apart from raw water pipeline, pump station and upgrading of treatment plant, the scheme will
also include the raising of Batu Dam. One of the components of work is the modification at the
existing spillway. The proposed hydraulic model study will aim to evaluate the hydraulic
performance of the modified spillway.
Batu Dam is a 39m high zoned, earth-rock filled dam. Existing dam crest is at elevation 109.5mand it is proposed to raise the dam crest level to 110m. Existing spillway is located on the leftabutment. It has a side channel inlet structure with a 23m long crest at elevation 104.85m. The
chute is 145m long and ends with a 32.5m long stilling basin at invert level of 60m. A raw inlet
structure with overflow weir will be constructed ahead of the existing spillway. Overflow level isset at elevation of 106.7m. The design requirement is to ensure the integrity of the dam and
spillway is still intact under design Probable Maximum Flood (PMF) scenario.
2. Objectives
The main objective of the study is (i) to construct a physical model of the Batu Dam spillway,(ii) to investigate hydraulic behaviour of the spillway and also its ancillary structures under a
range of design discharges, and, (iii) to investigate the discharge capacity of the prototype meets
the design requirement and measures the hydraulic parameters in order to judge whether thedesign is feasible.
3. Scope of Study
The following scope of work is needed to make an appraisal of the capacity and erosion aspects
of the dam and the overall performance of the spillway as well as to make informedrecommendations of its hydraulic performance and proposed alterations.
i. Investigation of the spillway discharge capacity with respect to various reservoir levelsand the model discharge coefficient as well as requirement for flood release.
ii. To study the flow pattern and flow surface profile on the dam and in the bottom outlet fordifferent cases.
iii. Velocity and pressure measurements at all relevant points for different flow conditions.
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iv. Determination of the intensity of turbulence at different points on the weir, transitionalarea, chute and energy dissipater.
v. Energy dissipation and scouring study to assess the suitability of downstream bed andbank protection.
vi. Stage discharge curve for the spillway model.The model scale was set at 1:25 ratio and then tested under designed Probable Maximum Flood
(PMF) scenario up to 300 m3 /s (96 l/s in the test model). Water supply was provided by five
pumps with a maximum capacity of 16.7 l/s each and one pump with a maximum capacity of 50
l/s.
4. Methodology
i) The main thrust of the study primarily consists of physical modeling work. A scaled model of thespillway and all its ancillaries will be constructed.
ii) Upon construction of the model, trial tests will be conducted to determine its functionality.iii) Experimental works proceeds as soon as calibration results are satisfactory.iv) Subsequently data will be compiled data, process and analyze to simulate the actual (model) and
predicted (prototype) conditions of the spillway.
v) Simulations with respect to various reservoir levels and discharges to investigate effects of thevaried flow conditions will also be performed.
vi) Finally, detailed appraisal of the model results will be provided in order to evaluate overallperformance of the proposed spillway, and to suggest possible maintenance and improvement
techniques or alterations where required.
5. Results
The incoming flow is steady as it has been stabilized before reaching the inlet opening. Each change ofdischarge rate will require about 5-10 minutes for the water to stabilize (Refer to Figure 1).
Figure 1: Intake/Approach Channel
From test for the discharge of 96 l/s (prototype: 300 m3/s), it was observed that no freeboard was visible.
In fact the water sometimes overflows the transition portion (Refer to Figure 2).
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Figure 2: Transition Portion
Starting from discharge of 80 l/s (prototype: 250 m3/s), the water in the chute started to overflow
occasionally. At a discharge of 96 l/s (prototype: 300 m3/s), there was permanent overflow at the middle
section along the spillway chute (Refer to Figure 3).
Figure 3: Spillway Chute
From test showed that water already reached the existing ground level for discharge of 32 l/s
(prototype: 100 m3/s). The water went above the existing ground level if the discharge is greater
(Refer to Figure 4).
Figure 4: Stilling Basin
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6. Conclusion
From the tests performed, the transition portion and the spillway chute is adequate for the
original design discharge but the stilling basin (energy dissipater) is inadequate to cater for the
high discharge in the original design. The proposed overflow weir is not found to have anybenefit in terms of controlling high flows (prototype: 200 m3/s, model: 64 l/s) as there are no
difference in the results when compared to test conditions without the overflow weir installed.Therefore to cater for a discharge of up to 300 m3/s, it is recommended that the freeboard at the
existing transition portion be increased by at least 3m and the wall of the spillway chute at the
middle be increased by 2m. For the stilling basin, its recommended that bunds of 5m high beconstructed around the perimeter to prevent inundation of the surrounding grounds.
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PHYSICAL MODELING 3: STRUCTURAL STABILITY OF ROCK ARMOUR AS GROYNE
FOR BATU MANIKAR BEACHES, FEDERAL TERITORY OF LABUAN
1. Background
The project is known as Proposed Beach Erosion Mitigation Structures and Beach Nourishment Project
at Batu Manikar Beach, Labuan. The structure testing was design to investigate the stability of thestructure before the construction phase begins at the actual site.
Batu Manikar beach, situated at the west coast of Labuan Island is constantly exposed to the effects of sea
and swells emanating from the South China Sea. Over the years, the beach stretch has shown signs of
erosion; with the beach frontage area observed to slowly retreating to the adjacent coastal road network.The main focus of the coastal protection and beach nourishment project is to mitigate the ongoing coastal
erosion thus prevent damage and loss of the existing coastal areas.
2. Objectives
The objective of the study are summarize below:
i. To evaluate the stability of the proposed structure under various design parameter;ii. To assess the suitability of armour rock in the proposed design;
iii. To assess the scouring impact around the structure.3. Scope of Study
There are 3 units of 200m length groyne having a spacing of 730m and 810m from north to south
respectively, to be constructed along the Batu Manikar beach. The groyne are made up of two layers of
rock armour, namely primary and secondary layers which will be placed over the core material with a
layer of geotextile as the under layer. The primary layer is made up of 1,400 2,400kg granite with more
than 50% comprised of 1,900kg armour, while the secondary layer is made up of 120kg -190kg granite.
The 200m length of groyne will be constructed and extended into the sea at the right angle to shoreline.The designed crest level is +2.2m MSL with side slopes of 1:2 and 1:3 for the trunk sections and head
sections respectively.
The cross-sectional profile of the tested groyne is shown in Figure 1..
Figure 1: Groyne cross section for the testing
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4. Methodology
The model was constructed in the wave flume. The construction started with the marking of cross
sectional profile on the flumes glass panel (Figure 2a). The marking includes the height and width of the
structure for each layer. The tested water level was also marked on the glass panel to ensure accuratewater level throughout the tests. Afterwards, the structure layers were constructed using the selected
gravel size (Figure 2b).
After the construction stage, testings for the structure were be run according to the parameters shown in
Table 1 below:
Table 1: Tested design parameters
Figure 2a: Marking process Figure 2b: Structure to be tested
Test 01 Test 02 Test 03 Test 04
Model Scale 1:10 1:10 1:10 1:10
Water Depth (m) 0.74 - (normal) 0.8 - (extreme) 0.8 - (extreme) 0.8 - (extreme)
Wave Height Max - Measured 1.685cm 1.702cm 1.701cm 1.705cm
Groyne Structure Weight
- First Layer 1.4kg - 2.4kg (with 50% more than 1.9kg) 1.4kg - 2.4kg (with 50% more than 1.9kg) 1.2kg - 2.0kg (with 50% more than 1.6kg) 1.2kg - 1.6kg (with 50% more than 1.4kg)
- Second Layer 120g-190g (without Geotextiles) 120g-190g (Geotextiles) 120g-190g (Geotextiles) 120g-190g (Geotextiles)
Test Duration 12 Hours 12 Hours 12 Hours 12 Hours
Data Set on Wave Generater
- Water Depth (m) : 0.74 0.8 0.8 0.8
- Wave Height (m) : 0.3 0.3 0.3 0.3
- Wave Period (s) : 3 3.2 3.2 3.2
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5. Results
The overall test results are tabulated in Table 2 and Figure 3 below.
Table 2: Tested parameter and observation
Model Scale 1:10
Water Depth (m) 0.8 - (extreme)
Wave Height Max - Measured 1.705 cm
Test Duration 12 Hours
Groyne Structure Weight
- First Layer
1.2kg 1.6kg (with 50% comprised of more than
1.4kg)
- Second Layer 120g-190g (with Geo-textiles)
Data Set
- Water Depth (m) : 0.8
- Wave Height (m) : 0.3
- Wave Period (s) : 3.2
Observation: After testing
No movement for the 1st
layer stone
Critical movement in the front section, almost 80 % of stone moved to the back section
Sand in front of the structure was 25 % scattered to the back section, showeing high
potential of erosion
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20 cm
20 cm
30 cm
18cm
18cm
30 cm
18 cm
38 cm
15 cm
Figure 3: Structure and sediment movement summary (extreme condition)
Before Test:
1.4kg-2.4kg,
no color
After Test:
1.4kg-2.4kg, no
color 120g-190g, Green =
Before Test:
1.4kg-2.4kg,
no color
After Test:
1.4kg-2.4kg, no
color
120 -190
After Test:
1.4kg-2.4kg,
yellow
120 -190
Before Test:
1.4kg-2.4kg,
yellow
Before Test:
1.4kg-2.4kg,yellow
After Test:
1.4kg-2.4kg,yellow
120 -190
Before Test:
1.4kg-2.4kg,
yellow
After Test:
1.4kg-2.4kg,
yellow
120 -190
Before Test:
120g-190g,
Red-
Bottom=137 c
After Test:
120g-190g,
Green=102 Blue
= 9 cs
After Test:120g-190g,
Green=3pcs
Blue = 17 cs
Before Test:120g-190g,
Red-
Bottom=83 cs
Before Test:
Sand
After Test:
120g-190g,
Green =7pcs
Blue = 15pcs,
After Test:
120g-190g,
Blue = 1pcs,
Before Test:
Sand
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6. Conclusion
The proposed model structure seems to be stable under normal test condition. Nevertheless, a large
amount of armour rocks were displaced when the model was tested under extreme test condition,
particularly in the middle section and near the front toe area. It is therefore proposed that a larger armourrock size be used for the middle section and toe area of the proposed groyne structure to enhanced the
overall stability.
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PHYSICAL MODELING 4: FLOOD MODELLING EVALUATION IN RIVER
MEANDERING CHANNEL UNDER TIDAL EFFECT FOR SUNGAI SELANGOR
1. Background
Basically flood can occur at any reach of a river due to different factors. In the upstream area it usually
caused by the discharge which exceed bankfull flow and that discharge cannot be sustained by rivercross section and river bed. Whereas flood occur in estuary area is caused by the tidal influences.
However, at the middle stretch of the open channel the occurence of flood is more complex to explainbecause of the combination of both factors.
Presently there are still lack of research on open channel hydraulics which is under the tidalinfluenced. One of the main reasons to the lack of research in this area is the limited data available
such as water level and flow along the river bed. The difficulty to produce rating curve in the tidal
influence area also influence the calibration process. Therefore, only one value is normally used inhydraulic analysis, such as highest spring tide which will result in very high water level and is
inaccurate.
2. Objectives
The objective of the study can be describe as follows:
i. To reduce flooding problem along the river by introducing cut off at the downstream.ii. To assess the floodplain and water level for various flow conditions and tidal influence
3. Scope of Study
i. To construct physical model at National Hydraulic Research Institute of Malaysia. Thisincludes choice of materials, physical model scale, evaluating and setting up the instruments.
ii.
Gathering the available data of Sungai Selangor for the simulation in the experiment. Runningthe physical experiment covering flow from low to high without tidal influence under low
tide, mean sea level and high tide and flows with tidal effect. Figure 1 shows the Flowchart ofthe study process
Figure 1: Flow Chart of the Study Process
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4. Methodology
Physical model which was developed covering the tidal influences area. The non distorted scale of1:100 was used in the physical model after considering the practicality of the size in term of spaceavailable, construction cost and time required for the construction.
The overall size of physical model is 10m x 40m and with a scale of 1:100. Figure 2 shows schematic
diagram of the model and Figure 3 shows the overall view of the constructed model.
Figure 2: Schematic diagram of physical model
Figure 3: Overall view of physical model from upstream
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Simulation process was carried out and the result of each experiments was recorded. The experimentswas done under different scenarios, at different flow rates and tides conditions where the readings was
recorded at eight (8) stations in the physical model as shown in the Figure 2. Cases of simulationscarried out are shown in Table 1.
Table 1: Test Cases
Case no Tide condition Flow (l/s)
1 Without tidal effect 1 , 2, 3, 4, 5, 6, 7, 8
2 With tidal effect 1 , 2, 3, 4, 5, 6, 7, 8
3 With tidal effect & cut off 1 , 2, 3, 4, 5, 6, 7, 8
5. Results
The experiment were carried out for various scenarios as describe above. The data of water level and
velocity for each experiment were recorded at eight (8) identified stations with eight different values
of flows. At each location three (3) readings were taken for velocity i.e at the middle and two sides ofthe channel and one (1) reading for water level i.e at the middle of the channel. Flow and velocity
were taken for three (3) different water levels (fixed) at the downstream i.e low water, mean sea and
high water. For the tidal effect one reading for water level and velocity were taken. These levels are
based on the tide data taken at the refered locations. Outcome of the analysis obtain from physicalmodeling were analyse.
Figure 4 shows the extend of the flooded area, for the original layout the experiment shows the water
start to overflow the bank when flow is 2l/s and flooded when flow is 3l/s and worsen when the flowincreases. As for the cut off section the experiment shows the water start to overflow the bank when
flow is 3l/s and flooded when flow is 4l/s and worsen when the flow increases.
Figure 4: Flood Plain - Comparison on observed flooded area without cut off and with cut off
under tidal effect for 5 l/s flow
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Figure 5 and 6 shows the plot ofwater level increases as the flow inc
Figure 5: Plot of water level vs fl
Figure 6: Plot of water level vs fl
6. Conclusion
The analysis shows that the water
velocity was inconsistent and fluctuit also shows that the cut off may a
not totally solved it. The experimunder all tested conditions.
ater level versus flow for 5 l/s discharge. As shoreases for both without and with cut off.
w under tidal effect for all station taken in flood
cut off
w under tidal effect for all station taken in floodoff
level increases as the flow increases and causes
ates and does not directly dependent on flow. Fromble to help alleviate the flood problems to certain
ent also shows that the flood does not occurs at t
Station A
Station B
Station C
Station D
Station E
Station F
Station H
Station G
4
wn below that
plain without
plain with cut
the flood. The
the experimentxtent but does
e downstream
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PHYSICAL MODELING 5: STRUCTURE STABILITY TESTING FOR ARMOUR
ROCK REVETMENT DESIGN AT TANJUNG PIAI, JOHOR DARUL TAZIM
1. Background
The study site is a mangrove swamp of 1.8 km long that forms part of a pocket beach in the
southern tip of Peninsular Malaysia. Recently, as the hinterland of the Sg Pulai is beingdeveloped into various water resources schemes, and the construction of port facilities for
deep draft vessels is being implemented, the coastline at the surrounding the studyt site is
observed to be eroding at a high rate. Mangroves are falling due to the erosion of the soil
underneath them. The likely cause of the bank erosion is the reduced sediment supply fromthe hinterland and the dredging of ship transportation channel that divert the course of
sediment supply to the mud flat of the project site. A re-adjustment of the coastline has beeninitiated, with the tendency of beaches along this hook-shaped bay receding inland.
Rock revetment and soft rock are two systems of coastal protection suggested to address this
coastline development phenomenon. They protect the beach from further erosion andsafeguard the mangrove in the State Park and prevent intrusion of seawater into the
agriculture land established behind existing coastal bunds. Where erosion is serious and hasremoved entire mangroves that form the first line of defence for the beach, stone revetment is
incorporated to contain the wave attack and break-up the wave energy within the revetment.Where the coastline is still sheltered by mangrove trees, soft rock is used to line the fringe of
mangrove forest and to reinforce the morphology of the coast.
2. Objectives
The main objective of the study can be described as follows:
1. To assess the stability of the design structure with a various condition.2. To indentify the adverse impact of the seabed around the structure.
3. Scope of Study
i. Preliminary assessment by extracting information from reports related to the studyarea.
ii. Data collection & hydro graphic survey to ensure the similarity between model andprototype.
iii. Layout plan of the scaled model in the flume for each cases test.iv. Preparation of flume and material depending on the layout plan and cases designv. Wave calibration to get the scaled design wave height.
vi. Model construction at the design wave height location.vii. Structure testing by running the scaled design wave height and period for certain
duration depending on the cases; and setup the observation point for analysis
purposes.
viii. Analysis processes using a video/camera to observe the model (stone revetment)movement before and after each test.
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4. Methodology
The model scale was set at 1:7 ratios and then tested under 20 ARI and 100 ARI conditions,as shown in Table 1 below.
Table 1: Test parameter for revetment model
Prototype Model
Duration 3 day 27.2 hour
20 ARI wave 1 m 14.3 cm
100 ARI wave 2 m 28.6 cm
Wave period 3.6 s 1.4 s
MSL 0.373 m 5.3 cm
MHWS (20 ARI water level) 1.628 m 23.3 cm
HAT (100 ARI water level) 2.408 m 34.4 cm
Armour layer rock 200 kg (min) 0.58 kg (min)
450 kg (max) 1.31 kg (max)
Under layer rock 30 kg (min) 0.09 kg (min)
150 kg (max) 0.44 kg (max)
A method that is commonly used for quantifying damage in rubble-mound structure models is
by counting the number of individual armour units that have been dislodged. The movementcan be observed and noted, or more conveniently, video and photographic documentation can
be used to record test results. The method to describe the damage percentage is the use of theNd. Hudson (1959) defined damage as the percentage of dislodged armour units to the total
number of armour units:
Where:Ndisplaced = number of displaced stoneNTotal = total number of stones in that layer (section)
The damage is typically calculated for individual section. Typically displaced stones arestones which are displaced by more than one unit diameter (Dn50). Armour is considered a
failure when theNdis more than 10% damage.
Wave overtopping is usually assessed by collecting the overtopping water in overtopping
trays or tanks and measuring the overtopped water volume or mass. The number ofovertopping events can be assessed by a wave gauge at the crest of the breakwater or by
continuous water level measurements (volume or mass) within the overtopping tray or tank.
5. Results
The results were tabulated in Figure 1 and Figure 2 below.
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Before After
Small movement but not significantly for the 1st
stone layer. Its showedthe structure was stable with appropriate stone weight.
2nd
layer are stabilized by using the geo-textile as a basic layer by wrapped
this layer. No movements because of the geo-textile tend to hold the stonewithin it.
The overtopping seems not happen under this current water condition.
Figure 1: Test result for 20 ARI wave scenarios
Before After
It was found the 1st
layer rock were moved significantly especially at thefront slope of the structure after the increment 100% of the wave height and
32 % of water level. The damage percentage = 7.12%
2nd
layer remain stable as previous test.
The overtopping was occurred for this case. The height structure seems notsignificant to protect the shoreline during a certain period of time.
The overtopping rate= 1.856 l/m/s
Figure 2: Test result for 100 ARI wave scenarios
6. Conclusion
The current revetment design is capable of protecting the shoreline area up to 100 ARI wave
condition. Even though there was some movement of the armour rocks, the amount did not
exceed the 10% damage percentage limit, which was the set damage threshold.
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PHYSICAL MODELLING 6: STUDY OF WABCORE ARTIFICIAL REEF STABILITY FOR
WAVE BREAKER FUNCTION
1. Background
In recent years, artificial reefs have become an increasingly attractive alternative for coastal
protection. Artificial reefs can be used to protect or restore beaches and at the same time create anenvironment conducive for the growth of marine life. The WABCORE (refer to Figure 1), a
composite system of concrete units developed by NAHRIMs researcher, is one such product
designed for this dual purpose and provides an alternative to the use of rocks as construction material.
The WABCORE units can be configured into several coastal and bank protection systems such as
groynes, wave breakers and retaining walls. The first WABCORE structures in the form of stackingartificial reefs were deployed near Teluk Panuba, Pulau Tioman, Pahang in September 2005.
Following this successful application of WABCORE units as a coral host, the WABCORE was
further tested for its function as wave breaker with the purpose of creating a calm foreshore
environment for another section of a beach. This configuration of WABCORE as wave breakers arealso intended to help build up a section of the beach to reduce erosion.
Figure 1: The WABCORE Artificial Reef
2. Objectives
The objective of the study is to (i) verify the stability of the WABCORE as potential wave breaker,
and (ii) to evaluate needs for improvement and optimization of the proposed WABCORE design aswave breakers.
3. Scope of Study
The scope of study is as follows:
i. Examine the stability of wave breaker cross sectionsii. Measure the wave height at different position of the section area;
iii. Asses the displacement of WABCORE units before and after each testsiv. Visual observations for scour evaluation and sediment accumulation capabilities of the
structure
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4. Methodology
The models of WABCORE wave breaker were constructed at a scale of 1:2. The blocks are 0.25m inheight per block, and made of concrete with void areas to allow for permeability. The water depth
will be designed at approximately -0.75m, allowing 0.25m crest between top of structure to thecorresponding designed water level. The rows of WABCORE blocks was placed with a distance of
approximately 1mm in the model in order to ensure that the rows do not provide unrealistic support
for each other.
The incoming waves were determined by means of wave gauges positioned in a way allowing for
separation of the incoming and reflected wave conditions. Additional wave gauges were positioned
close to and behind the structure. The test program includes two different heights of a WABCOREprofile. A 1-layer and a 2-layer structure were studied, modeling a coastal protection profile and a
wave breaker profile at shallow water. Maximum wave height of 0.5m and wave period of 5 secondswas generated. Each test was run equivalent to 5 hours in nature.
For the majority of the tests the seabed in front of the structure was made as a fixed bed not allowing
for scour. This is to avoid the model structure to fail because of scour before the stability can bestudied. However, a test series was included, where qualitative assessments of the scour risk will be
made by performing tests with a sand bed in front of the structure. It should be stressed that damage tothe structure related to geotechnical settlements or to structural strength of the individual unit were not
modeled in this study. A layer of modeled geotextile mat was laid to help assessment of theanticipated sand trapping capabilities of the model.
The test program includes three test series:a. Test series 1: Tests with the one layer structure. Fixed bed in front of the structure.b. Test series 2: Tests with the two layer structure. Fixed bed in front of the structure.c. Test series 3: Tests with the one layer structure. Moveable (sand) bed in front of the structure.
Figure 2: Testing of WABCORE stability in progress
5. Results
Initial results showed that WABCORE artificial reef proved to be stable during all the tests.
WABCORE was able to reduce the significant wave height thereafter to about 30%. Displacementand movement of some of the WABCORE units were observed by photos taken before and after eachtest, most notably at the left and right section of the alignment. These movements was possibly
enhanced by reflected wave action from the wave guide located at both side of the basin, as nosignificant movement occurred in the middle section (Refer to Figure 3a and 3b).
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Figure 3a: 2 layer WABCORE before testing Figure 3b: 2 layer WABCORE after testing
Visual observation and photos evaluation also showed only minor scour and possible degradation of
the sand layer in front of the structure during test series 3. Interestingly, the WABCORE wasobserved to accumulate substantial amount of sediment into its inner part (Refer to Figure 4). This
may be greatly influenced by the incorporation of voids in the WABCORE design.
Figure 4: Side view showing sediment accumulation along the whole stretch of WABCORE
wave breaker alignment
The observed uplift forces were not great enough to topple the structure in both 1-layer and 2-layer
tests, and so they remained stable throughout testing. It was also observed that without reinforcement
the possibility of stress and fatigue cracks on WABCORE would be likely, therefore it wasrecommended that reinforcement be retained in the prototype.
6. Conclusion
WABCORE artificial reef has demonstrated initial stability element required topotentiallyfunction asa wave breaker. It is recommended that a detailed study of wave transmissions and overtopping flux
be carried out in the wave flume to further assess the overall performance of the WABCORE. The
capability of WABCORE to trap sediment may prove advantageous in self-consolidating the structure
in the long run. Subsequently, the effect and possibility of varying the size of WABCORE voiddiameter and/or position to achieve optimum design efficiency as a wave breaker needs to be
evaluated further.
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PHYSICAL MODELING 7: THE DEVELOPMENT OF H-BLOCK FOR RIVER BANK
PROTECTION
1. Background
River serves as an important source of water and supports livelihoods. River is also essential fortransportation, acts as a defensive barrier, source for hydropower and recreational activities. However,
rapid development involving indiscriminate clearing of land has caused increase in river discharges
resulting in river bed scouring and bank erosion. This phenomenon has lead to river bank failures,
contributing to large amount of sediments into the river, loss of land and degradation of river waterquality.
One of the solutions to control the erosion and sedimentation problem is by protecting the river bank
using products such as H-Block. The development of H-Block is undertaken by the Research Centre
for River Management, National Hydraulic Research Institute of Malaysia (NAHRIM).
2. Objectives
i. To invent an innovative product for river bank protectionii. To spearhead the invention of water resources related products through long term R&D
efforts
3. Methodology
The development of H-Block involved three phases namely, the design stage, the physical modeling
and field tests. Once the design has been accepted, physical modeling with a series of tests andmeasurements follows. The physical modeling works are being carried out in the Hydraulic and
Instrumentation Laboratory of NAHRIM which provides sufficient facilities and equipment for these
purposes.
The tested physical model parameters:
Model Scale 1:10
River Width 2 metersMaximum River Depth 0.5 meters
Maximum River Flow 100 liters/second (l/s)River Sand Size 100 micron
A series of physical model testing was carried out to test the performance of the product, some ofwhich are as follows:
a. Test run for hydraulic channel without H-Block with flows of 80l/s, 30l/s and 15l/s for 24hours until bank failure. Bank slope is set at 1:1.
b. Test run for hydraulic channel with H-Block without lock system for flows of 15l/s and 30l/sfor 24 hours until bank failure. Bank slope is set at 1:1 and 1:2.
c. Test run for hydraulic channel with H-Block and lock system for flows of 15l/s and 30l/s for24 hours until bank failure. Bank slope is set at 1:1 and 1:2.
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Figure 1: H Blok model construction ready for testing
4. Results
Result of the test run is summarized in Table 1 below.
Table 1: Summary of tested flow parameter
Measurement Low Flow High Flow Flow Difference
Point Test 1 Test 2 Test 3 Test 1 Test 2 Test 3 High Flow Low Flow
1 0.125 0.109 0.125 0.265 0.093 0.245 26% 12%
2 0.127 0.109 0.127 0.247 0.225 0.242 24% 13%
3 0.129 0.074 0.129 0.247 0.219 0.171 24% 13%
4 0.130 0.111 0.129 0.233 0.219 0.252 23% 13%
5 0.129 0.123 0.130 0.266 0.236 0.260 26% 13%
6 0.125 0.119 0.130 0.250 0.207 0.255 25% 12%
7 0.120 0.107 0.123 0.256 0.234 0.259 25% 12%8 0.118 0.117 0.123 0.232 0.237 0.292 23% 12%
9 0.121 0.117 0.125 0.241 0.242 0.264 24% 12%
The H Blok was observed to be successful in reducing the velocity of flow when constructed
at the river bank model (refer Figure 2). This may due to the unique element of the structure
itself which provide extra roughness element and also voids for permeability allowance.
During testing for high flow conditions, movement of H Blok was detected at the river
meandering section, whereas at the straight section H Blok was observed to be stable.
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Figure 2 : Flow velocity before and after H Blok instalation
5. Conclusion
H Blok was considered successful in reducing the velocity of flow. The stability of H Blok
very much depends on the river morphology e.g. width, shape, geotechnical aspect, and bank
slope selection, with 1:1 slope giving a more favorable result. The joint spacing of the H Blok
during construction needs to be considered carefully due to possibility of failure during high
flows, particularly at the meandering section. The possibility of incorporating an interlocking
feature for installation of H Blok at this critical river section needs to be studied further.
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Other physical modeling studies conducted:
1. Study On Local Scour at Complex Pier in 2D Flume (University Putra Malaysia - December2008)
2. Study on General Sand Dispersion Pattern in Coastal Basin (June 2008)
3. Breakwater Study On Muddy Coast For Mangrove Replanting in Parit Hj Dorani, Sabak Bernam,Selangor Part 1 & Part 2 (FRIM & JPSM - May 2010)
4. Structure Stability Test for Semi-Swath Boat Model Fasa 1 in 2D Flume (UiTM - July 2010)
5. Analysis of Dry Sieving on Sediment Distribution Pattern for Pangkor Island (Pusat HidrografiNasional - July 2010)
6. Experiment on Sediment Settling Velocity for Muddy Coast of Sungai Haji Dorani (March 2010)
7. Experiment on Sediment Settling Velocity for Fresh Water of Sungai Kuyoh (March 2010)
8.
Structure Stability Test for Revetment in Johor State in 2D Flume (March 2010)
9. Study of Rainwater Harvesting System First Flush Effect (August 2010)
10.Evaluation of the Laboratory Performance of Field Offtake 150mm Diameter with Flexi-Gatesand Float Type Automated Flow Control Valve and Flat Regulator for Flow Control and
Measurement in Tertiary Irrigation (University Putra Malaysia) *
11. Study of Lift and Drag Balance With Models : Characteristics of Flow Around Two VaryingDiameter Cylinders and an Aerofoil (Multimedia University)*
12.Physical Modelling Study of Terengganu Airport Extension*
*Ongoing projects