Q. Explain the Maximum spacing of piles?

One of the factors which affect the distribution of loads from the structures to each pile is assumption of flexibility of the pile caps in design. A pile cap may be modelled as a flexible or a rigid element based on their relative stiffness. For the pile cap to be presumed as rigid the stiffness of pile cap is infinite relative to that of soil/pile system and deformations within the cap aren't considered due to its rigidity. Conversely for the pile cap to be designed as flexible, internal deformations of pile cap would take place. 

In a number of design guidelines, maximum spacing of piles is specified to limit the length between adjacent piles so that assumption of rigid pile cap can be justified.