You could be hitting on something here. Instead of pouring monolithic you could use prefab blocks that are filled in. I have used that technique to repair a cav

You could be hitting on something here. Instead of pouring monolithic you could use prefab blocks that are filled in. I have used that technique to repair a caved basement where cinder block replacements were filled with concrete and rebar. There is a similar system using foam blocks that act as forms and are left in place. Menards sells them (and may own the manufacturer).