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TSUNAMI RECONSTRUCTION WITH GEOSYNTHETICS IN COASTAL AREAS
AND WATERWAYS
by: Prof. Dennes T. Bergado
School of Civil Engineering
Asian Institute of Technology
Khao Lak Coastal Erosion
Before After
Coastal Erosion by Tsunami
The fury of the December 26, 2004 tsunami is still evident in the wreckage of this oil station at a fishery cooperative at Ban Nam Khem
(from Bangkok Post)
Coastal Erosion by Tsunami
Geotextiles, Geotubes & GeocontainersFor Marine Engineering Applications
IntroductionThe raging current
n River Ouveze, Europe (1992)
n 15 m high wall of watern 38 dead
Geotextiles, Geotubes & GeocontainersFor Marine Engineering Applications
IntroductionErosion by waves
Geotextiles, Geotubes & GeocontainersFor Marine Engineering Applications
IntroductionToe erosion leading to
landslides
n 1,300 dead from Hurricane David (1979)
Geotextiles, Geotubes & GeocontainersFor Marine Engineering Applications
IntroductionThe fury of waves
Polymer Background
n geosynthetics are really “geopolymers”n feedstock is natural gas reacted to form
resin in a flake formn mixed with additives into a formulationn manufactured into a particular type of
geosynthetic material
Geosynthetic (GS) Materials
n geotextiles (GT)n geogrids (GG)n geonets (GN)n geomembranes (GM)n geosynthetic clay liners (GCL)n geopipe (GP)n geofoam (GF)n geocomposites (G C)
n majority are made from polypropylene fibersn standard textile manufacturingn woven (slit film, monofilament or multifilament)n nonwoven (needle punched or heat bonded)n characterized by an open and porous structure
n unitized, woven yarns or bonded strapsn structure allows for soil “strike-through”n bidirectional – equal strength in both directionsn unidirectional – main strength in machine directionn focuses entirely on reinforcement applications, e.g.,n walls, steep slopes, base and foundation reinforcement
n all are made from high density polyethylenen results in parallel sets of ribs as a integral unitn biplanar – flow is equal in all directionsn triplanar – flow much greater in machine directionn function is always in-plane drainagen surfaces must be covered; usually with GTs
n function is always containmentn represents a barrier to liquids and gasesn many types: HDPE, LLDPE, fPP, PVC, EPDM, etc.n manufactured rolls are field seamedn required by regulations for waste containmentn new applications in hydraulics and private development
n its really buried plastic pipe!n function is always drainagen HDPE and PVC most commonn both can be smooth walled or corrugatedn corrugated HDPE growth is enormous
n EPS or XPS in block formn lightweight fill on soft or sensitive soilsn relieves lateral pressure on wallsn also used for insulation of frost-sensitive soils
n array of available productsn GT/GM; GT/GG; GT/GN; etc.n considerable ongoing innovationn primary function depends on final product
Roles of Geosynthetics
§ Separator
§ Reinforcement
§ Drainage
§ Filter
§ Energy absorber
§ Container
§ Barrier
2h:1v3h:1v
Mirafi PP80L
Armour Rock80 - 300 kg
-0.2+0.3
-1.93
1m
Mirafi Geotube
n Allowed use of sand as core fill material of breakwater
n Over 1 km ofGeotubes (theoretical diameter of 2.65 m) used
n Breakwater to protect habitat for birds
n Armour rocks placed as permanent cover to Geotubes
Lake Marken, Netherlands
MIRAFI GeotubesCore material for breakwater, Lake Marken,
Netherlands
MIRAFI GeotubesCore material for breakwater, Lake Marken,
Netherlands
MIRAFI GeotubesCore material for breakwater, Lake Marken, Netherlands
MIRAFI GeotubesCore material for breakwater, Lake Marken, Netherlands
MIRAFI GeotubesCoastal protection dyke, Sea Isles City, USA
Building
Road
GeoTube
Prevents storm wavesfrom inundatingshoreline and loss ofsand into the sea
Previous road
Sand Dune
3.65m
1.6m
ScourApron
Sea Isles City, US
MIRAFI GeotubesCoastal protection dyke, Sea Isles City, USA
Sea Isles City, US
MIRAFI GeotubesCoastal protection dyke, Sea Isles City, USA
MIRAFI GeotubesCoastal protection dyke, Sea Isles City, USA
MIRAFI GeotubesCoastal protection dyke, Sea Isles City, USA
Sea Isles City, US
MIRAFI GeotubesCoastal protection dyke, Sea Isles City, USA
MIRAFI GeotubesCoastal protection dyke, Sea Isles City, USA
MIRAFI GeotubesCoastal protection dyke, Sea Isles City, USA
MIRAFI GeotubesGroyne field for coastal protection, Bald Head Island, USA
N
Hand Drawn: not to scale
Geotubesè 3 mile long barrier island
è South facing beach experience erosion since 1970’s. Emergency conditions started in 1994.
è Need express sln&consrt
è Extremely restrictive environmental regulations in North Carolina. Traditional ‘hard’ structures prohibited
MIRAFI GeotubesGroyne field for coastal protection, Bald Head Island, USA
Shore line Feb 1987, Receding
1992 10,000 ft of South Beach renourished with 360,000 yd3 of sand
1993 ( 18 months later )Entire nourishment plus additional natural material were completely eroded
Groynes proposedNorth Carolina Coastal resources prohibits ‘hardened structures’, hence 14 ‘soft groyneswere proposed
MIRAFI GeotubesGroyne field for coastal protection, Bald Head
Island, USA
MIRAFI GeotubesGroyne field for coastal protection, Bald Head
Island, USA
MIRAFI GeotubesGroyne field for coastal protection, Bald Head
Island, USA
MIRAFI GeotubesGroyne field for coastal protection, Bald Head Island, USA
n Geotube groyneinstallation costsn $550,000 ( mat. &
cont. )
n Geotube 500 ft apart
n Geotube 300 ft in length
n Entire project costn $2,934,000
n Work began in early Jan 1996n 650,000 yd3 of
material over 12,000 ft of beach front
MIRAFI GeotubesGroyne field for coastal protection, Bald Head Island, USA
Amwaj Islands Project, BahrainGeotubes as reclamation dykes to form artificial islands
Amwaj Islands Project
n Creation of artificial islands through reclamation to form 3,000,000 m2 of land
n Creation of 9.5 km if beach front
n To house 2,000 sea view homes, 2 marinas, 9 hotels, cinemas, restaurants, ice-skating rink and aqua park
Amwaj Islands Project, BahrainGeotubes as reclamation dykes to form artificial islands
Geotube as reclamation dykes
n Geotubes of constructed height 2.6m stacked in 2 tiers as reclamation dykes
n Later construction includes submerged reef breakwater 300m in-front of geotubes to create perched beach
MHWN = CD+2.2m
Geolon PP80L
Armour rock60 - 300 kg
3h:1v
Platform level = CD+3.6m
Sea bed level = CD-1.6m
Geotube
Geotextile
Amwaj Islands Project, BahrainGeotubes as reclamation dykes to form artificial islands
Geotube installation
n Laying of geotube
Amwaj Islands Project, BahrainGeotubes as reclamation dykes to form artificial islands
n Construction of lower geotube in progress
Geotube installation
Amwaj Islands Project, BahrainGeotubes as reclamation dykes to form artificial islands
n Competed lower level geotube
Geotube installation
Amwaj Islands Project, BahrainGeotubes as reclamation dykes to form artificial islands
n Construction of upper level geotube
Geotube installation
MiraCell is cellular confinement systems or technically called geocell.
It is a three-dimensional cell made of HDPE strips ultrasonically welded together to contain soil.
What is Miracell
Slope repaired with stacked geocell
Slope of the channel is lined with geocell. Above water line, the geocell are tufted and below water infilled with stones.
Gabions
Mattresses
GeotextileRevetment Filters
Existing soilFine filter
Coarse filterUnderlayer
Primary armour
Existing soil
Underlayer(s)
Primary armour
Geotextile filter
b) Revetment containing geotextile filter
Revetment consisting wholly of granular materials
a)
Geotextiles, Geotubes & GeocontainersFor Marine Engineering Applications
n Geotextiles are used as filters to replace granular layers
n Primary armour can be dumped rock, concrete blocks or wire mattresses or gabions
n Geotextile filters are the most economical solution for revetment filters
Revetments
Water
Water Water
Concrete facing
Retained soil
Retained soil Retained soil
Geotextile filter
Geotextile filter Geotextile filter
Rock armour Stone-flled gabions
Concrete facing
Rock armour Stone-filled gabions
Geotextiles, Geotubes & GeocontainersFor Marine Engineering Applications
n Gabion baskets confine smaller stones to resist erosion better than exposed stones
Geotextiles, Geotubes & GeocontainersFor Marine Engineering Applications
RevetmentsGabions and mattresses
n Concrete blocks may interlock for higher erosion resistance and allow easy placement
Geotextiles, Geotubes & GeocontainersFor Marine Engineering Applications
RevetmentsPrecast concrete units
n Shore attached breakwaters to protectharbour entrance
Dykes & breakwaters
Geotextiles, Geotubes & GeocontainersFor Marine Engineering Applications
n Shore attached breakwater to protect recreational beach front
Dykes & breakwaters
Geotextiles, Geotubes & GeocontainersFor Marine Engineering Applications
CONCLUSIONS
1) Erosion on coastal areas and waterways by Tsunami, Hurricane and Flood waves.
2) Geosynthetics are thin, flexible, sheet-like materials most suitable for earth retention, erosion control and coastal/channel protection.
3) Geosynthetics are reliable and easy to install
4) Geosynthetics are lightweight with minimum maintenance.
5) Geosynthetics have low handling and overall costs.