Lets say we have a very large and deep circular footing for a tall tower such as an industrial chimney or a wind turbine, and for convenience we want to pour it not at once but in sections. Can this be done, provided that we have sufficient dowels between the pour sections? Or it must be a single pour?
-Yes, it is possible and is routinely done.
A couple of concerns,
Massive concrete creates a huge amount of heat and thermal expansion, thus the elaborate systems of cooling the pour.
Also the curing under different climates is not good so careful planning is needed.
The cold joint should be placed far from a critical change in stress.
Since the footing is "large and deep", both the vertical and horizontal construction or expansion joints can be utilized to partition the concrete pour.
Note, other than the capability/capacity of the concrete plant and crew to produce and handle the concrete placement, the amount of heat generated during hydration needs to be evaluated, as it is usually the most important factor in determining the size and thickness of an individual pour, with the consideration of the available temperature control method employed.
Another factor affecting the thickness of the pour is the potential of aggregate separation when poured from the height. It can be difficult to vibrate the concrete uniformly and adequately, that usually the main cause for having honeycombs in the concrete.