tsunami reconstruction with geo synthetic

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


IntroductionErosion by waves


IntroductionToe erosion leading to

landslides

n 1,300 dead from Hurricane David (1979)


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 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


Sea Isles City, US

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


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

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


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


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


Geotube installation

n Laying of geotube


n Construction of lower geotube in progress



n Competed lower level geotube



n Construction of upper level geotube


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)


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


n Gabion baskets confine smaller stones to resist erosion better than exposed stones


RevetmentsGabions and mattresses

n Concrete blocks may interlock for higher erosion resistance and allow easy placement


RevetmentsPrecast concrete units

n Shore attached breakwaters to protectharbour entrance

Dykes & breakwaters


n Shore attached breakwater to protect recreational beach front

Dykes & breakwaters


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.

tsunami reconstruction with geo synthetic

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