pipe bedding material 1

[dsheth]

Is there a requirement to place bedding of a certain minimum thickness below a buried pipe? I am trying to find a source that says that if the soils under the pipe have sufficient capacity, then there is no minimum requirement for bedding materials.

 

[cvg]

depends on the type of pipe, existing soil conditions, depth and type of backfill. There are many "requirements", not the least are those of the owner or the agency issuing the permit.

 

[dicksewerrat]

All pipe manufacturers I have worked with require a bedding under the pipe. ASTM standards call for bedding. Just do it. You will not be sorry.
Bedding may be just rearranging the existing soil a little or importing new material. As CVG stated, it depends on what, where and the guy that writes the check.

 

[DRC1]

Pipe bedding is usually a sand that can be shaped to fit the pipe. The purpose of bedding is not to provide additional soil capacity but rather to insure the pipe is well supported, and to tranfer the load to the bottom of the trench as a relatively uniform load. This prevents damage to the pipe due to either point loads or uneven settelment. like Dicksewerrat said, do it, you won't be sorry. Generally it is not a significant cost of the work. If you are looking for details, check with your state's DOT. They will have standard specs and details with which local contractors will be familar.

 

[KRSServices]

I suppose my question is more basic. In some instances, I have forgone the requirement of "bedding" in soil conditions conducive to uniformly supporting the pipe. These areas have typically contained uniform sand in the trench and therefore bedding in this case was not required. I am not familliar with any other situations where this could occur.



KRS Services

http://www.krs-services.com

 

[Focht3]

If you have a coarse, clean sand that is naturally in a medium dense to dense condition, you should be fine. But I'd still scarify and recompact the first 8 inches or so to reduce the risk of 'hard spots' damaging the pipe.



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?"

 

[DRC1]

There are often areas where the native material would pass for bedding material. But if you dig a flat bottom trench and put the pipe in the trench, the pipe will not be well supported, esp. if the pipe has bells, such as RCP. If you feel the native soil is sufficent for the bedding be sure to specify that the contractor shape the bottom of the trench to fit the pipe after tamping. Generaly you want to to get about 30% of the pipe circumfrence in the bedding. Personally, I would probably over excavate slightly and use some of the excavated native material as bedding. I do agree on a lot of jobs there is a requirement to buy bedding material, when the native material would work fine.

 

[Fizzhead]

dsheth:

The purpose of specifying bedding is well described here by several commenters. The reason bedding is normally specified, even when native soils may appear satisfactory is quality control. Uniform bedding support is critical to long buried piping system life and reuse of native soils, removed, possibly screened, reapplied and satisfactorily compacted is a common practice. However, just laying piping in an excavated trench is asking for future problems and is not allowed in many piping standards.