Roadway embankment over a pipe line

[ylee]

Hi All,

I am seeking for tips from experienced engineer who has expriences with installing some type of pile foudnation box culvert to protect utililty line from settlement.

Here is my situation.
I am working on a roadway project, building an overpass bride over existing railroad near a train station. There are many railroad lines underneath the proposed structure. In addition to that a 72" sanitary sewer line is arcoss underneath(about 8-10 feet from ground surface)those railroads and proposed embankment. This sewer line has to be in service for 24 hours/365 days. The height of proposed embankement is about 30 feet.
The subsurface condition of this area is very poor (About 10 feet of very-soft clayey silt or silty clay underlain by another 20 feet of very-loose to loose sand). These materials are interbeded down to depth of almost 100 feet. Bedrock is located about 150 feet from groundsurface.

According to my settlement calculation, about 1.5 feet of settment is anticipated. Obiously, this sewerline will be affected by this settlement. A box culvert type of structure with pile foundation is one of my concerns as a solution.

Is there any other way to protect this sewer line?

Many thanks in advance,

Yong

 

[gandersen]

Yong:

I would be concerned about downdrag on the piles if you are anticipating that much settlement.

Is it possible to go over the top of the embankment and roadway with some type of syphon?

Glen

 

[MSEMan]

Have you thought of building your embankment out of polystyrene blocks? Its not done very much in the US, but I have seen a number of very successful projects in Scandanavia when I was working there a few months ago. The blocks are built to the slope angle (roughly and then overlain with fill to enable the embankment to be grassed.

The use of polystyrene will essentially eliminate the dead embankent loads and the subgrade settlement.
Check out this link:

http://www.mottmac.com/html/03/project.cfm?projectid=45&project=technology#

Good luck.

 

[BigH]

YLEE - I'll put my two cents worth - this is major project - I can't tell as to how extensive the area of concern is over the pipeline. In Jakarta and in Thailand they will actually support the road on a piled relieving platform. Normally these are not as high as 10m but you could work out a "box" for the embankment where most is air, then support the box and overlying fill on your piles. With all the load supported by the piles, you won't get much in the way of downdrag forces. For downdrag, if the tip is in a "yielding" stratum, the downdrag forces will be manageable as the tip can move too. Where downdrag has caused major pile problems is for piles driven to rock - a non-yielding material.

Geofoam blocks are used and are light - about 50m of blocks is same weight as 1m of soil. They use these for rail bridge abutments (Norway) and Utah has used them on the I-15.

 

[DRC1]

I would be concerned that it will be destroyed during construction. I would look at a temporary by pass through the construcion area and replacing the sewer as part of the project. Yes it is a major expense, but so could the failure of the sewer at the wrong time in the project.

 

[lallatin]

I also like the idea of geofoam blocks for minimizing settlement. I'm familiar with the I-15 project, and was involved with parts of it, and they had shallower depths to deal with, and started with an very elaborate wick drainage system to accelerate consolidation under loads during construction without surcharging, while all structures were pile supported. It doesn't sound like ground improvement is an option in your case. Woodward-Clyde's office in Salt Lake City would be a good place to start if you want to get expert advice on this subject. Your loads may only have a significant influence in a reasonable depth of material. All-in-all, MSEman's suggestion is a good one, in my opinion. Anyway, your project sounds like fun, and I'd enjoy having more information about it!