Pipe jacking size limitations 1

[DLukesh]

We are researching ways to place RCPs through an existing road embankment where an 8-foot diameter conduit already exists. Either two additional 10-foot ID conduits along side the 8-foot pipe or one 16-foot ID conduit are required to handle the flows. Hard, basalt bedrock may be encountered along the alinement.

Are there practical limitations on the maximum size of RCP that can be "jacked" through an embankment?

 

[Focht3]

Limitations? Yep. Basalt.

Seriously, a 10 foot diameter pipe is within the limitations of the larger pipe jacking contractors. But a 16 foot pipe diameter may not be - in your area. Site and soil conditions have a lot to do with the success of this construction technique. Have you checked with the local pipe jacking contractors?

If you think that you may encounter basalt - even the weathered variety - along the pipe alignment, you would probably be better off with hand mining the two smaller shafts. Delays to the pipe jacking scheme could result in very costly extras - resulting in a much higher cost than hand mining. Something to think about, anyway -



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora. See faq158-922 for recommendations regarding the question, "How Do You Evaluate Fill Settlement Beneath Structures?"

 

[Zambo]

I guess at 16 foot ID no pipe jacking cutting head would be provided and that a combination of jacking and hand mining would be used.

Zambo

 

[DLukesh]

I realize that the mixed face conditions may require hand mining; I am more interested if anyone has experience jacking 16-foot ID pipe into place after excavation at the face has occurred? What is the maximum size that has been successfully jacked? Will the conduit need to be cast in place after the opening is tunneled by traditional methods?

 

[cvg]

you need to look at the costs of manufacturing, transporting and jacking this large pipe versus the cost to line the tunnel in place. It may be cheaper to just install a tunnel liner