performance evaluation of river bank protection using jute geo-textiles abdul jabbar khan, mohammad...

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


Rip-rap

System-I System-II

Formation of Filter Cake

Geotextile

Large Particles

Fine Particles


Rip-rapGeotextile

Large Particles

Fine 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


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)


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


Fin

enes

s M

od

ulu

s

Comparison of FM of Chainage 1230 m

Stage

Location



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


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


Fin

enes

s M

od

ulu

s

Comparison of FM of Chainage 1070m

Stage

Location


Before Implementation 1st Monitoring

2nd Monitoring

Chainage : 1657 m Chainage : 1657 m

Chainage : 1657 m

GeotextileLarge Particles

Fine 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


Type of river Mild

Type of flow One way

Maxm velocity (m/s)

1.6


–


–

Rainfall (mm) 2471

Bank Soil Type Clayey Silt

Side slope 1:2


5.0


1.4m (minm)

12

1mCC Block (400×400×200)


Treated JGT


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



Type of river Mild

Type of flow Tidal

Maxm velocity (m/s)

2.5


5.05


0.03

Rainfall (mm) 2105

Side slope 1:3


9.72River bank prior to

implementation of the trial



Type of river Mild

Type of flow Both way

Maxm velocity (m/s)

1.5


3.35


-1.5

Rainfall (mm) 1734

Side slope 1:2


13.0River bank prior to

implementation of the trial

Ghaghat, RangpurCharacteristics Value

Type of river Mild

Type of flow –

Maxm velocity (m/s)

2.0


32.5


27.6

Rainfall (mm) 2931

Bank Soil Type Silty Sand

Side slope 1:2


3.0–4.0


1

2

1mCC Block (40 cm CUBE -60% or 30 cm UUBE -40%)


Treated JGT


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

performance evaluation of river bank protection using jute geo-textiles abdul jabbar khan, mohammad...

Documents