What are the advantages of using top-down approach in basement construction?

The advantages of top-down approach are listed below:

(i) The structures above ground can be carried out simultaneously with the structures below ground. This greatly reduces the time for construction.

(ii) By using this approach, settlement can be reduced.

(iii) Since the permanent columns and slabs can be utilized to support loadings during construction, it saves the cost of formwork.

Note: Top-down approach means construction of basement is carried out from ground level downwards

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.