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The six designs

Advantages Disadvantages

Pneumatic tumble gate, BMK
  • Straightforward
  • Reliable parallel systems (14 valves)
  • Simple construction
  • Sensitive to negative head
  • Silting up of valves and compartments
  • Underwater maintenance

Segment gate, NIWAS
  • Barrier can be closed even in extreme floodcurrent
  • Simple construction system with proven hydraulic and offshore techniques
  • Opened doors vulnerable to collision
  • Silting up of gate chambers
  • Gate chambers cannot be pumped dry (for maintenance)
  • Interference from shipping during construction (sill construction with railtrack on top of it)
  • Gate has to plough through sediment deposits

Hydraulic tumble gate, STORCOM
  • 24 independent valves (risk of failure small)
  • Takes up minimum amount of space
  • Valves, caissons and bottom protection under-dimensioned
  • Foundation techniques (as for tunnelling) applicable?
  • Maintenance awkward
  • Silting up of valves

Sliding gate, CHNW
  • Gates well protected when open
  • Gates easily accessible in drained door-chambers (for inspection and maintenance)
  • Simple construction system within field of experience
  • Interference from shipping during construction
  • Over-dimensioned
  • Most expensive solution

Boat-gate, CSNW
  • Insensitive to silting up
  • No moving parts below water (reliability and ease of maintenance)
  • Less easily controlled closing-process
  • Loads uncertain (has direct bearing on control of closing-process)

The winning design:
Floating sector, gate BMK
  • Doors well protected when open
  • Ease of inspection and maintenance in drainable gate chambers
  • Well balanced design
  • Entire load borne by single point (hinge)