Excavation and shoring question

[SFUVancouver]

I am curious to learn about different excavation and shoring techniques that are used around for world. What are the advantages and disadvantages of each technique and what factors lead to the decision to use one method over another?

In Vancouver we seem to exclusively use shotcrete for shoring. Horizontal piles are drilled into the pit wall to pin light-gauge rebar in place and shotcrete is sprayed on. Layer by layer the earth is removed, the piles are drilled, rebar placed, shotcrete applied and then they go deeper.

Here is an example from one of the deeper excavation pits in recent memory.

(My photo, taken February 13th, 2008)

Excavation is done using standard earth moving equipment.

(My photo, February 13th, 2008)

[Coldrsx]

^here in Edmonton our soil is too unstable downtown for that method. We use a more traditional I beam + wood plank method.

Essentially they put I beams 5-8' apart and as deep as the parkade will be around the perimeter. They then incase these with concrete at the bottom.

Once they start excavation, they place 3" (varies) thick planks horizontally between each I beam to hold the soil back. This continues all of the way down the pit and is left as a retaining wall which will butt up against the future concrete UG parkade.

pic to follow

[Coldrsx]

^

[Boris2k7]

I've seen a few different types in Calgary, some courtesy of the current boom

1. I-Beam + Wood Plank
2. Shotcrete
3. Slurry Wall
4. Caisson + Concrete

However, the use of the last three are almost exclusive to a pair of project U/C (shotcrete + caisson wall for The Bow, slurry wall for Le Germain Hotel).