Thrust block installed on top of pipe bend 1

[PEDARRIN2]

I do not deal a lot with thrust blocks - use mechanically restrained joints like Mega Lug - but ran into this "standard detail" that contravenes my previous understanding. The detail is from a fairly sizable municipality.

My understanding is thrust blocks rely on undisturbed soil to be the "immovable" object to absorb the momentum of the fluid flow changing direction. The approach shown in the detail basically wraps the fitting in concrete which does not absorb the force but rather "contains" it. The joint cannot flex or leak due to being encased in concrete. Thee is no undisturbed soil in the direction of the thrust.

Would like to know the thoughts of those more familiar with thrust blocks.

 

[bimr]

Most thrust blocks were installed to prevent lateral movement. This design appears to be using the weight of the thrust block to prevent vertical as well as lateral movement when the pipe has to be routed underneath another pipe.

Don't believe that the concrete is intended to keep the joint contained.

 

[LittleInch]

The thrust is vectored so a portion of it will be horizontal, hence the note in section AA.

But yes, it uses the weight to resist the vertical component.

It will partially restrain the joint, but that's not what the main issue is.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[hydrae]

We called is a gravity block and the detail I am familiar with puts all the concrete
below the pipe and uses loops of rebar around the fitting into the concrete with
j-hooks embedded into the concrete
The pipe will also have polyethylene encasement to allow access to the bolts in the future
if needed.

 

[fel3]

+1 for hydrae. For more information, see DIPRA's "Thrust Restraint Design for Ductile Iron Pipe" here:

https://assets.ctfassets.net/e4roza...nt_Design_for_Ductile_Iron_Pipe__English_.pdf

BTW, DIPRA's publication is not limited to ductile iron pipe.

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