RE: Buried pipe Trench

From: <Steve>
Date: Tue Aug 10 2004 - 05:26:00 EDT

Hi manjuantha k

I sometimes design the fill for trenches. With plastic pipes, a fill design is essential especially if the most economic pipe wall thickness is to be used and especially partial vacuums are to be experienced under transient conditions. Sometimes it is necessary with thinner wall steel pipes as well. There have been a number of theories developed for the fill design; don't take my word for it; just look in any number of books and you will find a number of articles on the internet. Part of the objective of fill design and compaction is to fully support the pipe around its entire perimeter. This makes it much harder to squash (buckle) the pipe due to traffic/occasional loads and vacuum conditions. Failure by buckling is nearly always of much greater concern than straight compressive failure. The purpose of the sand is to protect the pipe surface and to increase the effective soil modulus, also sometimes to assist in containing thermal expansion.

I suggest you do some further reading before making further general claims.

Cheers

Steve

-----Original Message-----
From: manjunatha kh [mailto:sagarmanjunath@yahoo.co.in] Sent: Tuesday, August 10, 2004 9:06 PM
To: PipingDesign@yahoogroups.com
Subject: RE: [PipingDesign] Buried pipe Trench

pipe trenches are filled with sand and loose earth and normally compaction is not done/required.
if there is any vehicular movement across the pipe trench then a different method is used. i.e. main pipe is protected with a sleeve pipe one size higher than the main pipe. also please note while using digger buckets/ shovels may damage the pipe, the coating/ wrapping / cathodic protection if applied.
this 250 mm is enough if the location is totally new & single and no other piping is existing.
how the compaction is going to help. it only increases the cost and extra stress on the pipe.
please clarify.
Steve McKenzie <mechproj@xtra.co.nz> wrote: you need some clearance at each side to compact the bedding material. In smaller sizes, width is determined by other factors such as shovel/digger bucket width joint making and compaction access.

Cheers

Steve

-----Original Message-----
From: manjunatha kh [mailto:sagarmanjunath@yahoo.co.in] Sent: Tuesday, August 10, 2004 7:16 PM
To: PipingDesign@yahoogroups.com
Subject: Re: [PipingDesign] Buried pipe Trench

the good engineering practice for trench width is the diameter of the pipe + clearence of 3" on either side of the pipe ( at one meter depth).

cckla <cckla@pd.jaring.my> wrote:Mr. Manjunatha kh,

Can I konw how you determine this (250mm) ?

Regards,
cckla

   250mm

   cckla <cckla@pd.jaring.my> wrote:Dear all specialists,

   Do you know the minimum width of the trench for a 100mm diameter pipe, which will be considered as embankment backfill ? Is there any standard formula to determine the trench width for embankment backfill for the various pipe size ? Please guide me.

   Thank you.

   Regards,
   cckla

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