In designing the axial capacity of mini-piles, grout may be taken into account in the contribution of axial load capacity. However, the total load capacity of min-piles may not be equivalent to the sum of individual capacity derived from grout and from steel H-section.
The reason behind this is that the vertical loads on mini-piles are shared among grout and steel sections based on their Young’s modulus and areas. Basically, in order to comply with strain compatibility criterion, the steel bars and grout will deform as a whole though they possess different stiffness. A case may occur in which the sharing of loads for grout may be too high which cracks the grout section and fails the mini-piles already before the whole pile section could attain the full design load which is assumed to be the sum of individual capacities. Hence, strain compatibility has to be checked in designing the vertical capacity of min-piles.
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.
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