following the answers

I have seen joins in some of the structure but the act was preferred to have a good foundation for the support.

Jointing the ground beam can increase the stiffness of foundation, it is good for upper struct. But u need to realize that if u join the ground beam, it's too many steel bar link together，especially the node of the beam struct. Too solve this problem, must take action in supervision in construction , and using vibrator to make the jointing more compacted.

If money is enough for testing, I advise u can use "small strain test"(the theory just like pile echo test), to analysis whether the node of ground beam got honeycomb or not.