Sea wall and its sustainability


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Sea wall and its sustainability

  1. 1. Seawalls and its sustainabilityPresented byShravan sharmaFRM MA-2 07
  2. 2. Introduction• Coastal defence structure – hard stabilization• Along the coast• Reinforced concret , boulders, steel, gabions,aluminium ,
  3. 3. Types1. Vertical2. Curved3. Mound
  4. 4. Most easy designing and constructionDeflect waves ,loose rubbles absorbenergyAdvantagesDisadvantages1. Can be under cut by high wave energy environment2. Not efficient in long term3. Prone to expensive damageVertical type
  5. 5. Advantage1. Prevent overtopping the w2. low reflected waves and much3. reduced turbulenceDisadvantage1.More complex design process.2.can scour material at the base of the wall causing them tobecome underminedRound type
  6. 6. Advantages1.Current designs use porous designs of rock, concrete armour.2.Slope and loose material ensure maximum dissipation of waveenergy.3.Lower cost optionDisadvantages1.Less durable.2.Shorter life expectancy.3.Cannot withstand or protect from high-energy conditions effectivelyMound type
  7. 7. FunctionsPrimary functionsAccessory function• Retaining soil andsurcharge loads behindwall .• Protection of shorelinefrom wave loads• Protect frontline beachesfrom storm surges,shoreline erosion andwave overtopping.• Habitate for a variety offauna
  8. 8. Design consideration• Direct wave force action• Uplift force imposed by wave action• Wave overtopping• Storm surge• Toe scour
  9. 9. • The uplift force imposed by wave action isan important factor that is frequentlyneglected by design professionals .• Leads to instability and undermines thelongevity of the Sea Wall structure
  10. 10. Stepped sea wall
  11. 11. Sea Wall Systems• System A: Gravity Wall• System B: L-Shaped Wall with Buttresses• System C: L-Shaped Wall with ButtressesSupported by Piles• System D: Diaphragm Wall System withHorizontally Spun Wall• System E: Soldier Pile System with HorizontallySpun Wall and Tie Back Anchors (ModifiedBulkhead Approach)
  12. 12. System A: Gravity Wall• It is extremely costly to build, especially when wall heightdictates significant development of the wall base• Requires consideration of significant wave generateduplift force• Relies heavily upon the weight of the wall when thatweight significantly decreases due to buoyancy effect
  13. 13. continue• Requires a very stiff base that can preventwall settlement, tilting or heavy toe scourthat affects wall integrity and stability.• Unviable option when bedrock elevation orelevation of other suitable basesignificantly varies along the wall length.
  14. 14. System B: L-Shaped Wall withButtresses• More economical than a Gravity Wall and easier toconstruct.• Buttress of the wall serves as a stiffening element for thewall itself, and allows some force redistribution in thewall based upon the stiffness of the tapered buttresselement• Same design stability issues as a GravityWall:Significant wave generated uplift force.
  15. 15. Continue• Heavy reliance on soil surcharge on thehill of the wall at the time when that weightsignificantly decreases due to buoyancy.• Requirement for very stiff base andpossibility of heavy scour that can affectwall stability
  16. 16. System C: L-Shaped Wall withButtresses Supported by Piles• A type of wall, a modification of System B, that has asignificant advantage over System B.• Does not rely, or relies much less, on the gravity of thehill surcharge.• Less susceptible to distress due to scour problem.• Stability of the wall depends upon the pile capacity toresist uplift and the effect of horizontal load.
  17. 17. ContinuePrice of the wall can be prohibitive
  18. 18. System D: Diaphragm Wall Systemwith Horizontally Spun Wall• Easy to construct• Lower cost of construction and more flexibility of thesystem, as compared to the same features oftraditional designs.• Wall stability is not dependent on the gravity load ofbackfill.• Wall stability is independent of gravity of thesurcharge.
  19. 19. Continue• Low effect of soil scour in front of the wall on wall systemdistress. Easy maintenance.• Lack of uplift pressure on the wall base or heel, as theDiaphragm system does not have a heel.• Horizontally spun continuous wall supported by DeepBeam Diaphragms. Wall Diaphragm provides support forloads applied in both directions
  20. 20. System E: Soldier Pile System withHorizontally Spun Wall and Tie BackAnchors (Modified Bulkhead Approach• easy to construct.• The front of is similar to the front wall of the D system• Design philosophy is not same
  21. 21. Continue• Elastic foundation to resist the wave load inlandward direction.
  22. 22. Continue• Lack of uplift pressure on the wall base.• Stiffness of the soil anchors and stiffness ofspecially modified backfill allows for the designof the retaining wall as a continuously spunhorizontally slab.
  23. 23. • Wall stability is not dependent on the gravityload of backfill.• Low effect of soil scour in front of the wall onwall system distress.• Easy maintenance.• Lower cost of construction and higheradaptability
  24. 24. Advantage of system D and E• The erosion of the soil around the front pile can be easilyremedied• Use of flowable fly ash fill that can easily restore erodedsoil around the pile to a preexisting or better condition.• Erosion is almost never critical and does not requireurgent attention and can be restored during normalbeach nourishment operations.
  25. 25. Issues…1. Sea level rise2. Modelling limitation
  26. 26. Conclusion• Control coastal erosion .• Long term – hard stabilization• Maintenance is needed• Cost –effective approach isrecommended• Unintentional harm to unprotected nearby shores
  27. 27. Reference cited• Vitaly B. Feygin ,Sea Wall Systems Structural Engineeringmagazine USA.• Yoshimi goda , Random seas and design of maritimestructures ; 3rd edition•