Originally Posted by nealtw
So you will be digging down on both sides of the wall?
You are concerned about the blocks falling while you are working under there?
Would the stone be big enough to be one block reaching inside to outside?
Here's a better illustration of what we are looking for in terms of a jack.
1. Remove a 20" wide top portion of the cement over the dirt to expose the bottom of the limestone wall.
2. Drill one or two holes in the dirt under the bottom of the wall.
3. Insert horizontal jack arms in the hole or holes.
4. Raise the arms using the jack.
5. Remove a 20" wide column of dirt.
6. Insert cement footer.
7. Build block column.
8. Fill in most of the gap between the underside of the limestone wall and the top of the block wall. This will require temporary spacer wood to be placed next to the horizontal jack arms so they are not cemented into the wall.
9. Remove jack arms.
10. Remove temporary wood spacers.
11. Fill in the remaining space or spaces where the jack arms or arms were.
12. Repeat the process for the next section.
In regards to your questions:
We will digging from the inside only.
Yes, we are concerned about the bottom of wall giving way.
The limestone is of various sizes and are fit together like a 3D puzzle held together with mortar. There are no stones which would span the entire depth of the wall. There are no stones which would span the width of area to be excavated.