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Temporary wood shoring

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shacked

Structural
Aug 6, 2007
176
I am the EOR for a single family residence addition/remodel. The addition is a semi-subterranean garage attached to the existing house.
From the beginning on the project the soils engineer said that no shoring will be required since bedrock is relatively shallow. Also he outlined in the soils report that he was to observe the excavation of the garage and this is to be done in sections and slot cut.

The contractor/homeowner did not do this and he excavated a 7.5ft vertical cut right next to the existing house.
Now that it comes time for the geo to verify the soil at the bottom of the excavation he will not provide a memo for this to the city because he wants shoring. As you can see from the picture the vertical cut exposes a mixture of sandstone and rocks.

In the back of the soils report there are 2 figures that outline temp shoring loading, but no other recommendations.
I spoke with him and he was reluctant to tell me what loading that I should design the temp shoring for because the active pressure is now not active as there is most likely movement.

The contractor/owner wants me to design wood shoring with bracing instead of steel piles and wood lagging because that is too expensive.

What are your guys thoughts on this situation?
 
 https://files.engineering.com/getfile.aspx?folder=44a0872a-7761-4d31-a26e-7198b35fc8b6&file=20230928_101634.jpg
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My thoughts:
[ol 1]
[li]The geotech doesn't seem impressive.[/li]
[li]Too late to install soldier beams and lagging.[/li]
[li]Most of the completed excavation is not in bedrock.[/li]
[li]Should not have installed the reinforcing steel in front of an unshored excavation.[/li]
[li]Remove the reinforcing steel and place a stabilizing berm against the excavated face.[/li]
[li]While partially removing the berm in horizontally short lifts, soil nail and shotcrete the previously excavated face in lifts until subgrade is reached.[/li]
[li]Reinstall the reinforcing steel and build the addition.[/li]
[li]If the soil nail wall is designed as a permanent retaining wall, the new addition's foundation wall needs to support vertical loads only. If the soil nail wall is temporary, but left in plce, the foundation wall needs to support lateral earth and surcharge loads plus vertical loads from the addition.[/li]
[li]Yes, this is expensive.[/li]
[li]Yes, the existing pictured condition may remain stable without any excavation support - but for how long?[/li]
[li]Yes, the horse is already out of the barn and you probably already have an OSHA violation.[/li]
[li]That's what happens from hiring the wrong people.[/li]
[/ol]

 
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