Thrust Blocks 5

[DGrayPPD]

Can somebody explain to me when thrust blocks are required on underground piping?

For example, I have a 6" fire water storage tank fill line where the piping drops underground after a control valve and comes back up before it ties into the storage tank. All BW piping. The civil engineer is saying that we will need thrust blocks because we've always put thrust blocks on underground piping. Is this correct?

What practices help dictate when thrust blocks are needed?

If more information is needed, please let me know. I have attached a picture of the line to give better visualization.

 

[DGrayPPD]

I would be interested to hear some alternative suggestives to supporting the piping.

 

[rconner]

While I am more used to seeing flexible restrained joints used basically as hinges to handle normal differential settlements between structures and underground water pipes, as long as chosen coatings and linings for a butt-welded steel system with good foundation and bedding can tolerate the strain, I wonder if a specialist pipe support vendor could furnish some sort of spring principle support at any needed piers, to allow some movement and minimize the stress I worried a little about in seeing this layout?

 

[bimr]

Here is a design guide to provide some ideas:

design guide

 

[DGrayPPD]

Just following up with everyone. So now the latest debate is not whether the thrust blocks are needed at the bends but if they are needed as supports underneath for the piping to rest on.

Thoughts?

Does underground piping not normally just rest on the undisturbed soil?

Does it state anywhere in B31.3 or any code that concrete blocks are needed underground to act as pipe supports for the piping to rest on?