What are the functions of bedding under stormwater drains?

Bedding, which are normally made of granular materials or concrete, serves four main functions as suggested by O. C. Young and J. J. Trott:

(i) To enhance a uniform support under pipes in order to reduce the bending moment longitudinally;

(ii) To increase the load-supporting strength of the pipes;

(iii) For pipes with spigot and socket joints, it enables pipes to be supported along pipe lengths instead of pipe sockets. Otherwise, uneven stress may be induced and it may damage the pipes;

(iv) To provide a platform for achieving correct alignment and level during and after construction.

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.