OSHA Timber Shoring Design

[EngrJS1]

Hi,

I am studying how to design a timber shoring for an excavation using design tables from OSHA (

https://www.osha.gov/laws-regs/regulations/standardnumber/1926/1926SubpartPAppC).

I hope someone can answer the following questions:

1. According to the table, there are time when wales are not needed. If that's the case, how would the uprights be connected to the cross braces?
2. What do I do if the timber sizes in my country are too small for the ones specified in OSHA?

 

[PEinc]

1. For wales to not be needed, the verticals would need to be designed to cantilever above subgrade with driven embedment below trench subgrade or you would need to brace each vertical board, which is impractical.
2. Options: use more closely spaced horizontal wales, buy thicker vertical boards, slope a few feet of depth off the top to reduce the wall height,, brace individual vertical boards with trench jacks or hydraulic shores, use steel instead of timber, etc.

http://www.PeirceEngineering.com