shoring/sheeting for new elevator pit within existing basement

[Hoboneer]

A 6'-6" deep 24'x12' pit needs to be excavated in an existing basement. The clearance from slab to 1st floor joists is 9.5' so only a small minim excavator can be brought in. Is wood sheeting/lagging the only way to go or is there anything else that can be installed by hand or a small machine?

 

[jayrod12]

With only 9.5 feet of overhead clearance i think you're pretty well stuck with soldier piles and lagging. And even then you'll need to splice your soldier so it'll be an expensive deal. What about a secant or tangent pile wall? Could act as your pit walls if you poured a thinner flat face on the inside after excavation.

 

[SlideRuleEra]

Depending on soil properties, maybe vinyl sheeting driven by a (small) excavator mounted vibrohammer:
A typical Vinyl Sheet Piling Installation Manual

Unlikely this will be practical for the described conditions, but something to check on.

http://www.SlideRuleEra.net

 

[phamENG]

I did a similar project once, but it wasn't in a basement. Just the first floor of a masonry/concrete building on piles and we where we were adding a new elevator.

We cut out the floor several feet larger than the pit.
Drove helical piles around the perimeter to act as soldier piles.
Mini-ex dug out the pit. Wood lagging was installed on the soldier piles as we went down.
Once we bottomed out, we installed helical piles to support the shaft and then they put in some gravel and poured a mudslab.
Added waterproofing to the lagging.
Installed the floor rebar cage and poured the floor.
Installed the wall cages and internal form work and poured the walls.
Doweled into the remaining floor slab and poured our turndown onto the pit walls.
Masonry up to the top (5 or 6 floors, I think).