INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Jobs

Trenching for pipelines

Trenching for pipelines

(OP)
Pipelines are going to be placed in a trench of 4 m wide. The invert of pipes would be 5 m below the surface ground elevation. Ground is sandy silt (SPT=11), clayey silt (SPT=17), clayey sand (SPT=4) and below 7 m depth silty sand (SPT=15). Groundwater table is high.

We are using pre-fab cage with steel plates.

Could someone please advise 1-2 references/design manual to design the above trench - including heave, embedment length. Thank you very much.

RE: Trenching for pipelines

Lateral earth pressure for the sides with surcharging by equipment above.
Potential quick conditions from groundwater. Be careful of sand layer at bottom. Assume you will dewater well below this level.

RE: Trenching for pipelines

CalTrans Trenching and Shoring Manual - do a search - easily found

RE: Trenching for pipelines

(OP)
I went through the CalTran which referred to USSteel manual, which itself refers to W C Teng, 1962. I have still challenges on lateral distribution of pressures behind the cofferdam for the stratified soils. The above reference dopes not converge with Foundation Engineering Handbook's recommendations by T D Dismuke, 1991.

Wonder if there is a more recent reference which may take all the above into account. Thank you.

RE: Trenching for pipelines

Are your stratified soils so different? As you are building a shoring box, it will be strutted so a "braced" configuration would be appropriate - I think I'd simplify your "stratification" into a "worse" condition and a "best" condition - see how different they would be for your box design and then go from there. Be robust with your box design. You have never said at what depth the SPT 4 clayey sand is located - is it at the invert depth? Still, look at simplification to get a green or red light.

RE: Trenching for pipelines

(OP)
I have 1 m med dense sand over 2.8 m firm silty clay over 1.2 m loose sand. The sand continues under the base of excavation but become med. dense. For the 5 m to the excavation level, may a ask how you would suggest the worse and best conditions.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close