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Guidelines for Maximum allowed height of temporary shoring with out tie-backs
- Thread starter ayithi
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msquared48
Structural
Seems like too many variables here to come up with a general rule of thumb...
Pile size, pile spacing, active and passive pressures, surcharges, bridging effect reduction, concrete encasement, if any, to name the most relevant...
Mike McCann, PE, SE (WA)
Pile size, pile spacing, active and passive pressures, surcharges, bridging effect reduction, concrete encasement, if any, to name the most relevant...
Mike McCann, PE, SE (WA)
As Mike said, it depends. 12' is a good height to start considering bracing or tieback anchors. If the wall needs to be a bit taller. try sloping the top few feet and cantilevering the remaining 12'.
Added 12/30/2016
There are many engineers who will design cantilevered walls up to 20 or more feet high. While you can always find heavy enough and long enough soldier beams or SSP to cantilever this high, the performance may be questionable (too much lateral deflection means too much settlement behind the wall) and the extra steel and installation cost may be more than the cost of lighter, shorter, more closely spaced, soldier beams or SSP with tieback anchors added.
Added 12/30/2016
There are many engineers who will design cantilevered walls up to 20 or more feet high. While you can always find heavy enough and long enough soldier beams or SSP to cantilever this high, the performance may be questionable (too much lateral deflection means too much settlement behind the wall) and the extra steel and installation cost may be more than the cost of lighter, shorter, more closely spaced, soldier beams or SSP with tieback anchors added.
You may want to look at the CA Trenching and Shoring Manual. Some member of this forum recommended it in the past and found it very useful and practical. There is a chapter for unrestrained shoring systems. Also there are some guidelines about temporary retention systems.
Here is the link for the manual:
Here is the link for the manual:
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geotech_ben
Geotechnical
I prefer slopes. ![[thumbsup2]](/data/assets/smilies/thumbsup2.gif "[thumbsup2] [thumbsup2]")
If you insist on a wall, I second the calfornia trenching and shoring manual for sheet piles and soldier pile and lagging. I have used SupportIt computer program with pretty good success. Don't think about cantilever walls over 15 feet.
There are lots of other wall options depending on your project requirements. Cut or fill wall? It is a pretty endless subject if you don't provide the specifics for your particular project.
If you insist on a wall, I second the calfornia trenching and shoring manual for sheet piles and soldier pile and lagging. I have used SupportIt computer program with pretty good success. Don't think about cantilever walls over 15 feet. There are lots of other wall options depending on your project requirements. Cut or fill wall? It is a pretty endless subject if you don't provide the specifics for your particular project.
Wow. 12 feet, 15 feet.
I have succesfully finish couple projects with 6m, 7m, 9m (30 feet?) . Last one was in a hard limestone and pile socket was 9m too. Total displacement of the retaining system was 4cm!
Maybe it is because of different practices in different countries, however, I don't think this is engineering. We have to be bold.
I have succesfully finish couple projects with 6m, 7m, 9m (30 feet?) . Last one was in a hard limestone and pile socket was 9m too. Total displacement of the retaining system was 4cm!
Maybe it is because of different practices in different countries, however, I don't think this is engineering. We have to be bold.
I am not saying that deeper, cantilever walls cannot be designed and built. Sometimes they are the only possible or allowable solution. However, compare the cost for an extra tall, extra stiff, cantilevered wall with the cost of a tiedback or braced wall with much less steel, less drilling, and a greater soldier beam spacing. We do not have to be bold; we do have to consider cost.
Yes, PEinc younare dedinetely right.
For me, I use cantilever walls when I do not have any other choice or I need a permanent shorinf. I am not such a fan of permanent anchors, I do not trust most of the contractors in this issue. So using cantilever walls for permanent applications makes me feel more confident.
But as you said, cost comparison is another thing.
For me, I use cantilever walls when I do not have any other choice or I need a permanent shorinf. I am not such a fan of permanent anchors, I do not trust most of the contractors in this issue. So using cantilever walls for permanent applications makes me feel more confident.
But as you said, cost comparison is another thing.
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