Back filling tunnel

[plumbernoob]

I plan to tunnel under a slab foundation through clay soil. How should I back fill after the work is complete? Sadly, horizontal rammers don't appear to exist. Is topping the last 6 inches off with foam a decent idea?

Tunnel Dimensions:
Length: 6 ft
Width: 2 ft
Depth: 2 ft

 

[Chris]

Normally we backfill with slurry. Slurry is a really wet sand and cement mixture that hardens up but not hard li jj e concert, you can still dig through it later. For your case that might be overkill, I would just do the best you can packing dirt back in. Use a shovel handle to keep poking it into the little areas

 

[plumbernoob]

Thanks Chris. Your response is the cherry on top to my research. For all the videos and discussion about tunneling for sewer line repair there is shockingly little content about back filling. I'll have the guys do their best by hand paying special attention to the few feet around the edge foundation.

 

[Chris]

Sometimes a 2x4 or other object you can pack with will work. It will be hard to get to 90% compaction which is usually required but you will get close. Make sure your dirt is moist but not muddy.

 

[Mr_David]

I agree with Chris. It's only 2' wide and 2' deep. Your not going to loose any structural integrity of the slab.
Use a 2x4 and just pack it as you work your way out.
I have seen 4" to 4' gaps under slabs. The building sits on the footings

 

[frodo]

Sometimes a 2x4 or other object you can pack with will work. It will be hard to get to 90% compaction which is usually required but you will get close. Make sure your dirt is moist but not muddy.

Use moist sand packed into the holed

 

[journeyman]

You can get a powder puff for your back hammer. Use dry base and pack with powder puff