TOP-DOWN CONSTRUCTION METHOD

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TOP-DOWN CONSTRUCTION METHOD

• Use of diaphragm wall as the side support for
  the earth
• Construction progress upwards and downwards at
  the same time
• Savings in construction time
• Schematics and pictures give ideas on ongoing
  activities during construction

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Diaphragm Wall Installation
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Conventional Open-cut Bottom-up Construction
Method (For comparison with Top-Down Method)
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Conventional Open-cut Bottom-up Construction
Method (For comparison with Top-Down Method)
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Top-Down Construction Method
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Top-Down Construction Method
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Main Advantage of Top-Down Construction
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Details of Top-Down Construction Method
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Excavation to Level -1
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Excavate to Level -2
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Compaction and leveling of basement slab for
reinforcement and concrete works
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Circular ramp beam and wall supported on bored
column
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Excavation work of Level -3 in progress, use of
clamp-shell for exc.
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Excavation of Ramp Level -3 to - 4 in progress
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More excavation work in progress
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More excavation work of lower levels inprogress
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Above ground, structure works in progress
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Typical basement reinforcement slab ready for
concreting
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Concreting of basement slab for top-down
construction method
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Top-down construction work in progress
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Complete construction of project
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Another example of top-down construction
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Another example of top-down construction
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Conclusion

• Need careful consideration for use in HCMC since
  method is new here
• Ideal for 5 basements or more
• May need some soil improvement techniques and
  good dewatering system
• Equipment for these works may not be readily
  available in HCMC
• Handling of excavated soil material require
  planning, keeping in mind marine clay at upper
  level and silty sand at lower level