Replicating...

This will probably take some experimentation to get right, especially the angle to rotate by.
If you've copied my shape exactly, (which may not be possible, I may not have given enough info for that), then the figures given in the pic should work.
If not, either be very good at trignometry, or play with the angle to see what works.
When doing that I usually just replicate once, and undo if the reult isn't right.
Note that the Replicator is a sort of macro, it actually does several steps in one. When undoing, you have to undo each step.
Or just delete the replicated object...

1. Switch to Object Mode. If your wedge isn't selected, select it now.

2. Go to Menu->Tools->Replicator.

3. Fill in the values.

Notes:

• Number of copies: Well that's up to you. As noted above, if you're fiddling about getting the rotation value right, then set this to 1. That way you only have 1 copy to undo, not lots..
• The Translation, Rotation and scale lines each have 3 boxes. These are X, Y and Z values (in that order).
• Translation. We're only going to be moving each replication upwards, so set x & Z to 0.
    Check the W(idth), H(eight) and D(epth) values displayed above the Side View. For the wedges to line up exactly, enter the Height displayed there into the Y box.
• Rotation (the fun one). Again, we only want to rotate about the Y axis, so that's the only place a value should be entered.
• Rotate about the origin. (That was why all the fuss of getting the original box lined up with the Y axis.
• Scale isn't used in this little exercise, so lave as 1.0, 1.0, 1.0.

When you're happy, hit "Go".
Instant (well nearly) spiral staircase:-))

Almost there.
But we need to do a bit of tidying up....