Looks like a fun project- and the answer to your question will probably be a financial one. If you think that a repair can be made using existing portions of the foundation, then go for it, but if you have concerns, then rip it out. It may be less expensive in the end to build all new and not...
What is your task? Are you trying to determine settlement of the crane pad, or determine the allowable bearing capacity of the site for the lift?
The K value you previously determined will be the highest you could expect, as higher loadings will generally encounter higher increments of...
I agree with seeing an elevation view first. I would also be concerned with immediately tying the new foundation into the old one, especially if the addition is founded upon fill. The initial settlement of the addition could stress the existing foundation and cause cracking. You might...
If you intend on using a ring wall foundation (ie. no deep foundation elements) then there is generally no need to remove the cobbles or boulders. Excavate the cobbles that will interfere with the foundation and make sure the subgrade passes a proof roll. This is assuming that you are dealing...
What are you trying to model? For most gravelly or cobble-filled clay soils with more than 5-15% clay, the cobbles do not impact the strength or angle of internal friction. The cohesive strength of clay controls since there is no rock-rock interfacing. For simple settlement or capacity...
