18-12-2012, 03:00 PM
The Construction of Deep and Complex Basements and underground structures within extremely difficult urban environment
The Construction of Deep and Complex.pdf (Size: 5.75 MB / Downloads: 458)
Attributes that affect the construction of deep basement (Cont.):
Special performance requirements imposed
-Complete the whole or part of the work at a prescribed time or at stages for handing back to the client.
-Protect some facilities according to prescribed requirements during the course of work.
-Coordinate with some other contracts or contractors to have related works carried out in the same or in close proximity of site.
-The nature of work required exceptionally high quality or accuracy in performance.
-Very high liquidated damages requirements is imposed in the contract.
Besides, there are situations like:
•where a new basement is required to construct simultaneously to replace an old one.
•working under very fast-track schedule.
•some basement works need to be carried out at the same time with the new foundation or even with part of the future superstructure.
This situations will create very difficult coordination problemsthat involve various contractors and complicate the contractual position of the entire job..
There are many methods to construct large-scaled and deep basement
1.Deep basement can be constructed using some traditional ways such as cut & fill or bottom up methods. These methods are relatively economical and effective when dealing with certain jobs which are simpler in nature.
2.On the other hand where basement is going deeper and the surrounding environment getting more complex and sensitive, bottom up or combined method may be a more appropriate option to construct.
Commonality found in recent basement projects
•Recent basement projects are usually very deep (below 20m) and very big in size (say up to 10,000m2)
•Majority of the basements are constructed in a top-down manner. Some other methods such as combining top-down and bottom up, or combining open-cut and top-down arrangement, can sometimes be seen.
•Complicated coordination problems and teething arrangement often exist between various major contracts or other major building works.
•Layout planning especially in phasing and sectioning of the job forms a very important consideration mastering the success of the project.