Should a pipe or groups of bars be adopted as load carrying element of min-piles?

The design of mini-piles somehow differs from other traditional pile types. For instance, the design of most common pile types is controlled by the external carrying capacity. However, owing to the small cross sectional area, the design of mini-piles is limited by internal carrying capacity. Hence, the choice of suitable load carrying element is of paramount importance in the design of mini-piles.

For steel pipes used as load carrying element, it is of circular cross section with a high radius of gyration. Moreover, it possesses a constant section of modulus in all directions, it serves the properties of excellent column. Bars are suitable when pure axial loading is required in confined situation.

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.