Ductile Iron Pipe Supports

[washark]

What is the minimum required support for a sanitary sewer ditch crossing?

We have a 15' (at bottom with sideslopes of 2:1) ditch crossing with a 8" DIP sewer main. What concerns do I need to look check...hydraulics of stream or scour, pipe supports detail, length of pipe exposed prior to support, corrosion protection, ???

Site is in Southeast and freeze not a major concern. We could raise the sewer main from 1' above bottom, but can not lower (due to recieving manhole invert).

 

[KRSServices]

Am I reading this right? Is the pipe exposed in the ditch? Is it resting on the bottom of the ditch or requiring support at some elevation above the ditch bottom? Or is it crossing slightly below the ditch channel (top of pipe slightly below the ditch bottom)?

KRS Services

http://www.krs-services.com

 

[washark]

Currently we have pipe above bottom of ditch by 1'. It can be raised, but not lowered. It is a 8' deep channel/creek (more appropriate name then ditch). We need to check whether there is any normal base flow in channel, I imagine that has some bearing on this.

 

[KRSServices]

Protecting the pipe is relatively easy. You can wrap it, provide for a differetn material type through the crossing or encase it in another pipe. The crossing itself presents another challenge.

The pipe will effectively create an obstruction in the flow of the channel, and subsequently, it will have standing water. This water will either evaporate or migrate into the channel soils, which may eventually compromise the material supporting the pipe. A geotech could provide detailed analysis, but I would think that a layer of large fractured face rock with (dry portland) cement sandbags placed under the pipe in the ditch zone would be adequate. One consideration that must be evaluated will be the longterm settlement of the native soils versus the support structure to ensure that differential settling (causing a shear failure in the pipe) of the soils is minimized.

KRS Services

http://www.krs-services.com