ᐅ How to underpin a strip foundation?

Hello everyone,

I am currently planning the renovation of my basement. Due to the planned insulation and other work, I unfortunately need to underpin the existing strip foundation, as it is not deep enough.

Since I will not be excavating around the house from the outside, I have to carry out the underpinning from the inside.

Therefore, I would like to ask if anyone has experience with this and which tools you have used for it?

I would like to make this tough job as easy as possible, possibly using a mini excavator or similar equipment.

I look forward to your tips.

Thank you in advance.
Best regards,
Achim