Transcript PowerPoint - What is the SELOC Barrier?

Welcome
Demonstration of the Self Erecting, Low Cost Flood Barrier
The ‘SELOC’ Flood Barrier
Project team:
John Greenwood
Reader in Geotechnical Engineering
School of Architecture, Design and the Built Environment
Nottingham Trent University
Peter Atchison
Director
PAGeotechnical Ltd, Corby
Steve Corbet
Technical Director
Aecom Group (Faber Maunsell Ltd)
Current approaches to Flood
Defence
(Nottingham in old photographs 1944-1974,
Douglas Whitworth 1991)
Permanent walls hold back the
floods but we lose the river views
Current flood defence systems
Ironbridge flooding
Demountable barrier,
Shrewsbury
Demountable barrier
(Ref. Environment Agency – Stokes and May 2004)
ICE Tilt Dam
A low cost, self erecting flood barrier.
The idea:Float
Cover
tie
Flood
waters
Protective
slab
Geomembrane
Backfilled
trench
The flood and wave barrier
– construction sequence
Site selection and
investigation
d
d
d
Trench planned
d =width =depth
=height of protection
Trench excavated
d
d (tie)
d
d (tie)
d
Flexible geosynthetic
membrane, (typical
width = 3d) placed
against sides and
base of trench.
Ties connected to
membrane.
Trench backfilled.
Most of arisings
compacted back
into trench
Protective stabilising
slab placed on
trench fill.
Suitable rigid covers
attached to membrane
Suitable float attached
to each cover
(if needed for buoyancy)
Ties attached to covers
and linked to membrane
in trench
Operation checked
between closed and
open conditions
Note, in simplest form,
covers hinge on the
geomembrane.
Coarse gravel placed to
allow easy access of
water to float.
Barrier is now ready for
action
As water level rises,
float responds and
barrier rises restrained
by the tie.
As water level falls
again, barrier returns
to horizontal rest
position
The flood and wave barrier.
- Resting position
After flood,
barrier returns to
horizontal rest
position.
Use as walkway?
Lea Marston Trials
Funded by Stimulating Innovation for Success (SIS)
Site Surveying and setting out (4
th
Sept, 2007)
Initial Trial at Lea Marston Trial – Excavation starts (10
th
Sept)
Trough cut out in slope, Trench excavated, reference
plywood/timber edge installed
Membrane (Seaman XR5) prepared
40 mm pipe inserted through cut outs in fold in membrane
to attach ties
Trench backfilled with natural soil
Paving slabs placed for additional stability
Plywood covers attached – Gate hinges used in trial
Membrane folded over polystyrene floats held by batons.
Ties attached.
Covers fixed ready for action
Ground elevation change at ends of barrier compensated by horizontal
alignment change to permit free operation of covers.
Ready to pump water in
Successful retention of 600mm of water
A successful initial trial
The basics of the design
(Patent no EP 1880058 granted 31 Dec 2008)
Cover Decking or
polymer
Mechanical hinge
or membrane
hinge
Float
(if required)
Tie
Permeable
block
Edge kerb
Slab
Geomembrane
Backfilled
trench
Tie attached to
rod through
seam
The barrier at rest – used as a walkway
Design of the self erecting barrier as a retaining structure
(Student exercises)
‘ACTIVE’ FORCES
GRAVITY
FORCES
Total
vertical
pressure
‘PASSIVE’ FORCES
Effect.
horiz.
press.
Effect.
vert.
press.
Water
Press.
Total
vert.
press.
A
Pp
Kpd(b-w)
d(b-w)
Pw1
E
B
d
Pw4
dw
db
Effective
horizontal
pressure
wl
d
wl
Effective
vertical
pressure
Water
pressure
W
C
Pw2
ca
Pa
Pw3
D
d
dw +db
Pw5
dw
2dw
Pw6
BUOYANCY
FORCES
2dw
d(b - w)
Kad(b - w)
Consideration of flows beneath the barrier
A
h=d
B
E
Flow line
C
D
Equipotential
Impermeable
boundary
If k=10-5 m/sec, under head, d= 0.9m, Flow q= 14 litres/hr per m run.
Trench depth may be increased in very permeable ground
Current demonstration - production version
conceptual cover
design in
polyethylene using
Rotarymould
process.
Hinges slot in to
kerb unit
Timber pattern for covers
The team consider kerb options
Rotary moulded covers and hinge units
The kerb and hinge assembly
Test loading of the rotary moulded covers and hinge units
at NTU
Lea Marston Site Demonstration – September 2009
Trench excavated,- Straight section with end walls
Seaman XR5 Membrane – tie attachments
Membrane and ties positioned in trench
Ready for backfill
Backfilling commences
Natural soil backfilled and compacted
Bedding for paving slabs
Paving slabs positioned
Kerbs and covers positioned
End wall construction
Battens fixed to hold membrane to covers
Ties fixed
Site Demonstration
• Developments and Applications
Self erecting barrier used to increase effective height of existing
(or new) flood embankment
Membrane may be extended below
embankment to intercept groundwater
flows in more permeable strata
Basic Design – possible use of decking as Barrier covers
Applications
•
Flood protection where cost or visual intrusion precludes conventional
flood defences
•
Low cost alternative to demountable barriers
•
Increase the effective height of existing or new flood banks
(No additional fill or loading)
•
Secondary protection of local areas for ‘at risk’ cities such as
Hamburg or New Orleans
•
Temporary water storage
•
Low cost protection of low lying agricultural land
•
Protection around ‘hazardous’ storage tanks
•
Control of drainage – Diverting flood waters to safe storage areas
•
Help resist tsunami wave forces
SELOC Flood Barrier – Advantages
•
Control of (flood) waters at low cost
•
‘Low tech’ site construction – re-use of on-site materials
•
Self erecting (no dependence on mobilised manpower)
•
Preserves waterside landscape
•
Membrane intercepts and reduces groundwater seepage
•
Full professional technical support. Each ‘at risk’ site carefully assessed by Consulting
Engineers (AECOM) and SELOC applied only if it is the appropriate solution.
•
Can be designed to suit scale of flood protection (200 – 1000mm+) and protective
surfacing provided to suit the location (walkway/driveway etc,)
•
Varied applications - (Flood protection, water storage, tsunami protection etc.)
•
European Patent
‘Working Together’
Engineering in Harmony with the Environment!
Thank you for your interest today
The project team is grateful to the Environment Agency (Harvey Twivey) for
making the site and pumping facilities available for the trials at Lea Marston.
The financial support under the ‘EMDA’ Innovation Fellowship Scheme is
acknowledged with thanks.
We appreciate the support of our organisations and in particular the site help
and project input provided by:
NTU – Anton Ianakiev, Steve Goodman, Alan Chambers, Mark Flanagan
AECOM – Pete Jones (Site trial coordination), Dave Cartwright
PAGeotechnical – David Plumtree, Neil Salvedge
Rototek – Stuart Wright.
[email protected]
[email protected] (Peter Atchison)
[email protected]