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Welcome Demonstration of the Self Erecting, Low Cost Flood Barrier The ‘SELOC’ Flood Barrier John Greenwood Reader in Geotechnical Engineering School of.

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Presentation on theme: "Welcome Demonstration of the Self Erecting, Low Cost Flood Barrier The ‘SELOC’ Flood Barrier John Greenwood Reader in Geotechnical Engineering School of."— Presentation transcript:

1 Welcome Demonstration of the Self Erecting, Low Cost Flood Barrier The ‘SELOC’ Flood Barrier 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) Project team:

2 Current approaches to Flood Defence Permanent walls hold back the floods but we lose the river views (Nottingham in old photographs , Douglas Whitworth 1991)

3 Current flood defence systems Ironbridge flooding Demountable barrier Demountable barrier, Shrewsbury (Ref. Environment Agency – Stokes and May 2004) ICE Tilt Dam

4 A low cost, self erecting flood barrier. The idea:- Cover Protective slab tie Geomembrane Backfilled trench Float Flood waters

5 The flood and wave barrier – construction sequence Site selection and investigation

6 Trench planned d =width =depth =height of protection d d d

7 Trench excavated

8 Flexible geosynthetic membrane, (typical width = 3d) placed against sides and base of trench. Ties connected to membrane. d d d d (tie)

9 Trench backfilled. Most of arisings compacted back into trench

10 Protective stabilising slab placed on trench fill.

11 Suitable rigid covers attached to membrane

12 Suitable float attached to each cover (if needed for buoyancy)

13 Ties attached to covers and linked to membrane in trench

14 Operation checked between closed and open conditions Note, in simplest form, covers hinge on the geomembrane.

15 Coarse gravel placed to allow easy access of water to float. Barrier is now ready for action

16 As water level rises, float responds and barrier rises restrained by the tie. As water level falls again, barrier returns to horizontal rest position

17 The flood and wave barrier. - Resting position After flood, barrier returns to horizontal rest position. Use as walkway?

18

19 Lea Marston Trials Funded by Stimulating Innovation for Success (SIS) Site Surveying and setting out (4 th Sept, 2007)

20 Initial Trial at Lea Marston Trial – Excavation starts (10 th Sept)

21 Trough cut out in slope, Trench excavated, reference plywood/timber edge installed

22 Membrane (Seaman XR5) prepared

23 40 mm pipe inserted through cut outs in fold in membrane to attach ties

24 Trench backfilled with natural soil

25 Paving slabs placed for additional stability

26 Plywood covers attached – Gate hinges used in trial

27 Membrane folded over polystyrene floats held by batons. Ties attached.

28 Covers fixed ready for action Ground elevation change at ends of barrier compensated by horizontal alignment change to permit free operation of covers.

29 Ready to pump water in

30 Successful retention of 600mm of water

31 A successful initial trial

32 The basics of the design (Patent no EP granted 31 Dec 2008)

33 The barrier at rest – used as a walkway

34 Design of the self erecting barrier as a retaining structure (Student exercises) Total vertical pressure d d d Effective vertical pressure Effective horizontal pressure Water Press. Effect. vert. press. Effect. horiz. press. Total vert. press. Water pressure d(  b -  w ) 2d  w d  w +d  b K a d(  b -  w ) 2d  w d(  b -  w ) dwdw dbdb K p d(  b -  w ) dwdw B caca W E D C A P w3 PaPa  wl PpPp P w6 P w5 P w4 P w1 P w2  wl ‘ACTIVE’ FORCES GRAVITY FORCES ‘PASSIVE’ FORCES BUOYANCY FORCES

35 Consideration of flows beneath the barrier E D A B C Flow line h = d Impermeable boundary Equipotential 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

36 Current demonstration - production version

37 conceptual cover design in polyethylene using Rotarymould process. Hinges slot in to kerb unit

38 Timber pattern for covers

39 The team consider kerb options

40 Rotary moulded covers and hinge units

41 The kerb and hinge assembly

42 Test loading of the rotary moulded covers and hinge units at NTU

43 Lea Marston Site Demonstration – September 2009 Trench excavated,- Straight section with end walls

44 Seaman XR5 Membrane – tie attachments

45 Membrane and ties positioned in trench

46 Ready for backfill

47 Backfilling commences

48 Natural soil backfilled and compacted

49 Bedding for paving slabs

50 Paving slabs positioned

51 Kerbs and covers positioned

52 End wall construction

53 Battens fixed to hold membrane to covers

54 Ties fixed

55 Site Demonstration

56 Developments and Applications

57 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

58 Basic Design – possible use of decking as Barrier covers

59 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 Applications

60 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!

61 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. (Peter Atchison)


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