Missing bricks under chimney stack

[bgrey]

Hey guys. Digging out part of my patio and noticed under the chimney there is a void which is just soil. Is this normal? Should I be concerned? Does it need digging out and backfilling or am I best just leaving it?
Any advise or other experiences of this welcome. Mantle of bricks is about a foot under patio level. Thanks in advance.

 

[stevie888]

If you dig a bit deeper I think you'll the bricks corbel out from the main foundation

 

[Wayners]

Ash dump hole maybe.
I've got this foggy memory of holes at the back of chimney to aid in cleaning it out.

Maybe that?

 

[^woody^]

If you've scraped that soil out for no reason, best stop, refill the hole with concrete and then finish what you are doing around the walls.