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The use of prestressed tiebacks gets rid of the need of interior bracing. Prestressed tiebacks are anchored into rock or granular soils and excavation can be conducted by using powerful shovel instead of using hand excavation or other small excavators. It provides less restraint and allows free movement for excavation.
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.