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
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)
Introduction The raging current n
River Ouveze, Europe (1992)
n
15 m high wall of water
n
38 dead
Geotextiles, Geotubes & Geocontainers For Marine Engineering Applications
Introduction Erosion by waves
Geotextiles, Geotubes & Geocontainers For Marine Engineering Applications
Introduction
Toe erosion leading to landslides
Geotextiles, Geotubes & Geocontainers For Marine Engineering Applications
Introduction The fury of waves n
1,300 dead from Hurricane David (1979)
Geotextiles, Geotubes & Geocontainers For Marine Engineering Applications
Polymer Background n n n n
geosynthetics are really “geopolymers� feedstock is natural gas reacted to form resin in a flake form mixed with additives into a formulation manufactured into a particular type of geosynthetic material
Geosynthetic (GS) Materials n n n n n n n n
geotextiles (GT) geogrids (GG) geonets (GN) geomembranes (GM) geosynthetic clay liners (GCL) geopipe (GP) geofoam (GF) geocomposites (G C)
n n n n n
majority are made from polypropylene fibers standard textile manufacturing woven (slit film, monofilament or multifilament) nonwoven (needle punched or heat bonded) characterized by an open and porous structure
n n n n n n
unitized, woven yarns or bonded straps structure allows for soil “strike-through” bidirectional – equal strength in both directions unidirectional – main strength in machine direction focuses entirely on reinforcement applications, e.g., walls, steep slopes, base and foundation reinforcement
n n n n n n
all are made from high density polyethylene results in parallel sets of ribs as a integral unit biplanar – flow is equal in all directions triplanar – flow much greater in machine direction function is always in-plane drainage surfaces must be covered; usually with GTs
n n n n n n
function is always containment represents a barrier to liquids and gases many types: HDPE, LLDPE, fPP, PVC, EPDM, etc. manufactured rolls are field seamed required by regulations for waste containment new applications in hydraulics and private development
n n n n n
its really buried plastic pipe! function is always drainage HDPE and PVC most common both can be smooth walled or corrugated corrugated HDPE growth is enormous
n n n n
EPS or XPS in block form lightweight fill on soft or sensitive soils relieves lateral pressure on walls also used for insulation of frost-sensitive soils
n n n n
array of available products GT/GM; GT/GG; GT/GN; etc. considerable ongoing innovation primary function depends on final product
Roles of Geosynthetics § Separator § Reinforcement § Drainage § Filter § Energy absorber § Container § Barrier
Lake Marken, Netherlands n
n
n n
Allowed use of sand as core fill material of breakwater Over 1 km of Geotubes (theoretical diameter of 2.65 m) used Breakwater to protect habitat for birds Armour rocks placed as permanent cover to Geotubes
Armour Rock 80 - 300 kg -0.2
+0.3 v 3h:1
1m 2h : 1v
-1.93
Mirafi PP80L
MIRAFI Geotubes Core material for breakwater, Lake Marken, Netherlands
Mirafi Geotube
MIRAFI Geotubes Core material for breakwater, Lake Marken, Netherlands
MIRAFI Geotubes Core material for breakwater, Lake Marken, Netherlands
MIRAFI Geotubes Core material for breakwater, Lake Marken, Netherlands
Sea Isles City, US
Sand Dune
Building
3.65m
Road
Prevents storm waves from inundating shoreline and loss of sand into the sea
1.6m GeoTube Scour Apron Previous road
MIRAFI Geotubes Coastal protection dyke, Sea Isles City, USA
Sea Isles City, US
MIRAFI Geotubes Coastal protection dyke, Sea Isles City, USA
MIRAFI Geotubes Coastal protection dyke, Sea Isles City, USA
MIRAFI Geotubes Coastal protection dyke, Sea Isles City, USA
Sea Isles City, US
MIRAFI Geotubes Coastal protection dyke, Sea Isles City, USA
MIRAFI Geotubes Coastal protection dyke, Sea Isles City, USA
MIRAFI Geotubes Coastal protection dyke, Sea Isles City, USA
MIRAFI Geotubes Coastal protection dyke, Sea Isles City, USA
MIRAFI Geotubes Groyne field for coastal protection, Bald Head Island, USA
Geotubes è
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
N
Hand Drawn: not to scale
MIRAFI Geotubes Groyne field for coastal protection, Bald Head Island, USA
1992 10,000 ft of South Beach renourished with 360,000 yd3 of sand 1993 ( 18 months later )
Shore line Feb 1987, Receding
Entire nourishment plus additional natural material were completely eroded Groynes proposed North Carolina Coastal resources prohibits ‘hardened structures’, hence 14 ‘soft groynes were proposed
MIRAFI Geotubes Groyne field for coastal protection, Bald Head Island, USA
MIRAFI Geotubes Groyne field for coastal protection, Bald Head Island, USA
MIRAFI Geotubes Groyne field for coastal protection, Bald Head Island, USA
MIRAFI Geotubes Groyne field for coastal protection, Bald Head Island, USA
n
Geotube groyne installation costs n
$550,000 ( mat. & cont. )
n
Geotube 500 ft apart
n
Geotube 300 ft in length
n
Entire project cost n
n
$2,934,000
Work began in early Jan 1996 n
650,000 yd3 of material over 12,000 ft of beach front
MIRAFI Geotubes Groyne field for coastal protection, Bald Head Island, USA
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, Bahrain Geotubes as reclamation dykes to form artificial islands
Geotube as reclamation dykes n
n
Geotubes of constructed height 2.6m stacked in 2 tiers as reclamation dykes
Armour rock 60 - 300 kg
Geotube
Platform level = CD+3.6m MHWN = CD+2.2m 3 h: 1
Later construction includes submerged reef breakwater 300m in-front of geotubes to create perched beach
v
Sea bed level = CD-1.6m
Geolon PP80L
Geotextile
Amwaj Islands Project, Bahrain Geotubes as reclamation dykes to form artificial islands
Geotube installation n
Laying of geotube
Amwaj Islands Project, Bahrain Geotubes as reclamation dykes to form artificial islands
Geotube installation n
Construction of lower geotube in progress
Amwaj Islands Project, Bahrain Geotubes as reclamation dykes to form artificial islands
Geotube installation n
Competed lower level geotube
Amwaj Islands Project, Bahrain Geotubes as reclamation dykes to form artificial islands
Geotube installation n
Construction of upper level geotube
Amwaj Islands Project, Bahrain Geotubes as reclamation dykes to form artificial islands
What is Miracell
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.
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
Revetments n
n
n
Geotextiles are used as filters to replace granular layers Primary armour can be dumped rock, concrete blocks or wire mattresses or gabions Geotextile filters are the most economical solution for revetment filters
Geotextile Revetment Filters Primary armour
Existing soil Fine filter Coarse filter Underlayer a) Revetment consisting wholly of granular materials Primary armour Existing soil Geotextile filter Underlayer(s) b) Revetment containing geotextile filter
Geotextiles, Geotubes & Geocontainers For Marine Engineering Applications
Concrete facing Water
Geotextile filter
Retained soil
Concrete facing Rock armour Geotextile filter Water
Stone-flled gabions Water
Geotextile filter
Retained soil
Rock armour
Retained soil
Stone-filled gabions
Geotextiles, Geotubes & Geocontainers For Marine Engineering Applications
Revetments Gabions and mattresses n
Gabion baskets confine smaller stones to resist erosion better than exposed stones
Geotextiles, Geotubes & Geocontainers For Marine Engineering Applications
Revetments Precast concrete units n
Concrete blocks may interlock for higher erosion resistance and allow easy placement
Geotextiles, Geotubes & Geocontainers For Marine Engineering Applications
Dykes & breakwaters n
Shore attached breakwaters to protect harbour entrance
Geotextiles, Geotubes & Geocontainers For Marine Engineering Applications
Dykes & breakwaters n
Shore attached breakwater to protect recreational beach front
Geotextiles, Geotubes & Geocontainers For 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.