PERFORMANCE EVALUATION OF RIVER BANK PROTECTION USING JUTE GEO-TEXTILES
Abdul Jabbar Khan, Mohammad Shariful Islam, Abu Siddique, Roman Kabir and Shamima Nasrin
Dr. Mohammad Shariful IslamProfessor, Department of Civil Engineering,
Bangladesh University of Engineering and Technology (BUET) Dhaka-1000, Bangladesh
National Seminar on the Project: Development and Application of Potentially Important Jute Geo-textiles (CFC/IJSG/21)
1st April 2014, JDPC, Dhaka
River Bank Failure
Typical river bank failureEROSION IS CAUSED BY SOIL LOSS DUE TO HIGH SEEPAGE FORCE
EROSION IS CAUSED BY WAVE ACTION
Failed surface
Failed surface
Cause I
Cause II
Failure Mechanism of River Bank Erosion
Structural Measure – Revetments– Guide bunds – Boulders– Brick matressing– Geo-bag dumping
Common Practices for River Bank Protection
Biological Protection–Bank Vegetation–Wood piling–Willow posts
Rigid structural protection system is widely used.
Unfortunately our national budget is never sufficient which
confines rigid structural protection measures to the most acute
sections, never to the full length of the river bank or coastline and
embankment. This BANDAGE APPROACH compounds the problem.
The environments in which geotextile filters have to perform can be divided into three categories, based upon the flow conditions: a) Fairly steady unidirectional flowb) Reversing flow with a moderate cycle timec) Reversing flow with a very short cycle time
Where the flow is unidirectional - the filter effect is not confined to the geotextile but spreads to the adjacent soil.- some loss of fine soil particles occur through both aggregate based filters and geotextile based filters when they are subjected to water flow. - the loss of fine material from the natural soil will be greatest immediately adjacent to the geotextile sheet, leaving a zone where the remaining larger soil particles bridge over the geotextile pores. These comparatively large soil particles will restrain slightly smaller soil particles which will in turn restrain even smaller soil particles.
This causes the formation of a graded filter structure known as “Filter Cake” in the zone of soil in contact with the geotextile. After the formation of this soil filter cake, geotextile filter becomes redundant.
Protection Against River Bank: Formation of Filter Cake
Formation of Filter Cake
GeotextileLarge Particles
Fine Particles
Medium Size Particles
Rip-rap
Geotextile
Large Particles
Fine Particles
Medium Size Particles
Rip-rap
System-I System-II
Formation of Filter Cake
Geotextile
Large Particles
Fine Particles
Medium Size Particles
Rip-rapGeotextile
Large Particles
Fine Particles
Medium Size Particles
Rip-rap
ONCE THE FILTER CAKE FORMS, THE JGT FILTER IS NOT REQUIRED
ANYMORE. SO, BIODEGRADIBILITY OF JGT IS NOT A PROBLEM, (JMDC
2008).
System-III System-IV
River Bank Protection System Used by BWDB
Geotextile filter replacing a multi-layer granular filter in a bank protection system
Bonded rip-rap protection system for canal side
Extended toe of rip-rap protection system, to deal with scour
Locations of River Bank Protection Trials
1. Pathoraj, Panchaghar2. Ghaghat, Rangpur3. Gorai, Rajbari4. MBR Channel, Gopalganj5. Sakhbaria, Koyra, Khulna
1
2
3
4
5
Possibility of using JGT in 11 river bank sites were investigated. Among these, 5 sites have been selected for field trails, situated at various geographic locations with varying soil conditions. Sites are:
DETAILS OF SELECTED RIVER BANK SITES
Name of River
Location Facilitating
AgencyLength
(m)
Type of
Flow
Maxm velocity
(m/s)
HFL (m)
LFL (m)
Rainfall (mm)
SideSlope
Maxm Scour Depth
(m)
Pathoraj,Panchagar
Northern part
BWDB
500One way
1.5 63.5 60.7 2931 1:2 0.90
Gorai, Rajbari
Western part
100 One way
1.6 – – 2471 1:2 5.0
MBR Channel, Gopalganj
South part 200 Tidal 2.5 5.05 0.03 2105 1:3 9.72
Sakhbaria, Khulna
South-west part
400 Tidal 1.5 3.35 -1.5 1734 1:2 13.0
Ghaghat, Rangpur
Northern part
BWDB & SWO
750 One way 2.0 32.5 27.6 2931 1:2 3.0-4.0
BWDB: Bangladesh Water Development BoardSWO: Special Works Organisation
River Name Type of JGT used (gsm)
Condition of JGT
Pathoraj, Panchagarh 760 Bitumen Treated
Gorai, Rajbari 627 Additive Treated
MBR Channel, Gopalganj
627 Bitumen Treated
Sakhbaria, Koyra, Khulna
627 Bitumen Treated
Ghaghot, Rangpur 627 Untreated, Bitumen Treated Additive Treated
JGT USED IN RIVER BANK PROTECTION
Bitumen Treated JGT Additive Treated JGT
JGT USED IN RIVER BANK PROTECTION
Parameter Test Standard Unit Type of JGTDescription of Samples Untreated
(627 gsm)Bitumen
Treated (760 gsm)
Bitumen Treated (627
gsm)
Additive Treated (627
gsm)Mass per Unit Area ASTM D3776 gm/m2 567 1177 860 638Thickness ASTM D1777 mm 1.86 3.24 2.46 2.27
AOS, O95 ASTM D4751* μm 300-600 300-600 <75 300-600Vertical Permeability(2 kN/m2) at 20°C ASTM D4491 m/sec *
10-3 1.79 0.17 2.68 1.42
Grab Tensile Strength at 30°C ASTM D4632 N 710/745 – 630/840 675/550
Grab Tensile Elongation at 30°C ASTM D4632 % 21/61 – 18/22 30/32
Wide Width Tensile Strength at ASTM D4595 kN/m 20/17
35.4/23.3
17/23 20/18
Wide Width Tensile Elongation at ASTM D4595 % 11/9 – 15/17 12/12
CBR Puncture Resistance DIN 54307 N 2830 4130 2930 2990
PROPERTIES OF JGT USED IN RIVER BANK PROTECTION
Pathoraj River Bank, Panchaghar
Characteristics Value
Type of river Mild
Type of flow One way
Maxm velocity (m/s)
1.5
Highest flood level (m)
63.5
Lowest flood level (m)
60.7
Rainfall (mm) 2931
Bank Soil Type Sandy Silt
Side slope 1:2
Maxm scour depth (m)
0.90
River bank prior to implementation of the trial
DESIGN OF RIVER BANK PROTECTION: PATHORAJ RIVER
1
2
1mCC Block (40 cm CUBE -60% or 30 cm UUBE -40%)
100 mm thick khoa filter(40 mm to 20 mm & 20 mm to 5 mm), Well graded
Treated JGT
100 mm sand filter(FM 1.0 to 1.5)
Volume of Launching Apron = 3.0 cum/m
3 m
Pathoraj River Bank, Panchaghar
JGT Application: June-July, 20111st monitoring: January, 20122nd monitoring: April, 2013
MONITORING
PVC pipe with:• 1.20 m long • 50 mm diameter
0
10
20
30
40
50
60
70
80
90
100
0.00.11.010.0
Outside
Middle
Inside
% F
iner
Particle size (mm)
0
10
20
30
40
50
60
70
80
90
100
0.00.11.010.0
Outside
Middle
Inside
Particle size (mm)
% F
iner
RESULTS (GRAIN SIZE DISTRIBUTION)
At implementation time After six months of implementation
After twenty four months of implementation
Chainage : 1657 m
Chainage : 1657 m
Chainage : 1657 m
RESULTS (FINENESS MODULUS)
Chainage : 1190 m (beneath JGT)
Chainage : 1230 m (beneath JGT)
0.0
0.5
1.0
1.5
2.0
2.5
Init
ial s
tage
1st
insp
ecti
on
2n
d in
spec
tio
n
Init
ial s
tage
1st
insp
ecti
on
2n
d in
spec
tio
n
Init
ial s
tage
1st
insp
ecti
on
2n
d in
spec
tio
n
Outside Middle Inside
Fin
enes
s M
od
ulu
s
Comparison of FM at Chainage 1190 m
Stage
Location
0.0
0.5
1.0
1.5
2.0
2.5
Init
ial s
tage
1st
insp
ecti
on
2n
d in
spec
tio
n
Init
ial s
tage
1st
insp
ecti
on
2n
d in
spec
tio
n
Init
ial s
tage
1st
insp
ecti
on
2n
d in
spec
tio
n
Outside Middle Inside
Fin
enes
s M
od
ulu
s
Comparison of FM of Chainage 1230 m
Stage
Location
RESULTS (FINENESS MODULUS)
Chainage : 1657 m (beneath JGT)
Chainage : 1070 m (beneath SGT)
0.0
0.5
1.0
1.5
2.0
2.5
Init
ial s
tage
1st
insp
ecti
on
2n
d in
spec
tio
n
Init
ial s
tage
1st
insp
ecti
on
2n
d in
spec
tio
n
Init
ial s
tage
1st
insp
ecti
on
2n
d in
spec
tio
n
Outside Middle Inside
Fin
enes
s M
od
ulu
s
Comparison of FM of Chainage 1657 m
Stage
Location
0.0
0.5
1.0
1.5
2.0
2.5
Init
ial s
tage
1st
insp
ecti
on
2n
d in
spec
tio
n
Init
ial s
tage
1st
insp
ecti
on
2n
d in
spec
tio
n
Init
ial s
tage
1st
insp
ecti
on
2n
d in
spec
tio
n
Outside Middle Inside
Fin
enes
s M
od
ulu
s
Comparison of FM of Chainage 1070m
Stage
Location
RESULTS (FINENESS MODULUS)
Before Implementation 1st Monitoring
2nd Monitoring
Chainage : 1657 m Chainage : 1657 m
Chainage : 1657 m
GeotextileLarge Particles
Fine Particles
Medium Size Particles
Khoa filter
DISCUSSION
(1) Considering the first monitoring (investigation after six months), from the grain size distribution curves and FM it was found that in case of three samples, soil particles of the outside layer or near JGT are coarser than the particles of middle and inside soil layer. So, it can be said that, filter cake has been formed partially.
(2) Considering the second monitoring(investigation after two years), from the grain size distribution curves and FM it was found that in case of one sample, soil particles of the outside layer or near JGT are coarser than the particles of middle and inside soil layer. So in this case it can also be said that, filter cake has been formed partially.
Gorai River Bank, Rajbari
Characteristics Value
Type of river Mild
Type of flow One way
Maxm velocity (m/s)
1.6
Highest flood level (m)
–
Lowest flood level (m)
–
Rainfall (mm) 2471
Bank Soil Type Clayey Silt
Side slope 1:2
Maxm scour depth (m)
5.0
River bank prior to implementation of the trial
1.4m (minm)
12
1mCC Block (400×400×200)
100 mm thick khoa filter(40 mm to 20 mm & 20 mm to 5 mm), Well graded
Treated JGT
100 mm sand filter(FM 1.0 to 1.5)
Extended portion of JGT = 1 m
14.0 m
0.7m (minm)
DESIGN OF RIVER BANK PROTECTION: GORAI RIVER
Gorai River Bank, Rajbari
JGT Application: June-July, 20131st monitoring: October, 2013
1st MONITORING 31.10.2013
JGT was found in good condition
MBR Channel, Gopalganj
Characteristics Value
Type of river Mild
Type of flow Tidal
Maxm velocity (m/s)
2.5
Highest flood level (m)
5.05
Lowest flood level (m)
0.03
Rainfall (mm) 2105
Side slope 1:3
Maxm scour depth (m)
9.72River bank prior to
implementation of the trial
MBR Channel, Gopalganj
Sakhbaria, Koyra, Khulna
Characteristics Value
Type of river Mild
Type of flow Both way
Maxm velocity (m/s)
1.5
Highest flood level (m)
3.35
Lowest flood level (m)
-1.5
Rainfall (mm) 1734
Side slope 1:2
Maxm scour depth (m)
13.0River bank prior to
implementation of the trial
Sakhbaria, Koyra, Khulna
Ghaghat, RangpurCharacteristics Value
Type of river Mild
Type of flow –
Maxm velocity (m/s)
2.0
Highest flood level (m)
32.5
Lowest flood level (m)
27.6
Rainfall (mm) 2931
Bank Soil Type Silty Sand
Side slope 1:2
Maxm scour depth (m)
3.0–4.0
River bank prior to implementation of the trial
1
2
1mCC Block (40 cm CUBE -60% or 30 cm UUBE -40%)
100 mm thick khoa filter(40 mm to 20 mm & 20 mm to 5 mm), Well graded
Treated JGT
100 mm sand filter(FM 1.0 to 1.5)
Volume of Launching Apron = 3.0 cum/m
3 m
DESIGN OF RIVER BANK PROTECTION: GHAGHAT RIVER
1) It is found that partial filter cake was formed within six month of JGT application.
2) Although Bitumen treated JGT was decomposed in six months time, the additive treated JGT was found in good condition.
3) So, it can be said that JGT is effective until the filter cake is formed for natural protection of the river bank.
CONCLUSIONS
Thank You
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