Box Culvert - Settlement under a Embankment

[CWEngineer]

I am looking for some advice/guidance on a Box Culvert design under an Embankment that might have two different soils beaneath, which might cause differential settlement.

Is there maximum differential settlement that a box culvert can tolerate? In terms of structural design, do you guys have any advice on what needs to be done, to design this box culvert for differential settlement?

Thanks

 

[VoyageofDiscovery]

Consult a geotechnical engineer and up to an inch of differential settlement is acceptable from a structural point of view.

VOD

 

[wiktor]

Is there maximum differential settlement that a box culvert can tolerate?
No, there is no specific value limiting the amout of the settlement. The limiting factors will be the amount of distortion the structure could handle without damage or distress.
Typically, in the ares where the differential settlement is expected, the culvert should be divided into section with some kind of flexible joint, allowing for some movement. Other option will be to use prefabricated corrugated metal culverts (pipe or arches), which could handle very large differential settlements.

 

[civilperson]

A culvert or dam outlet structure with curved vertical alignment to match the future predicted settlement is a normal design method to assure a straight positive grade at the future time when 90% of consolidation settlement has occurs. The portion built over alluvium and with the greatest fill loads is humped up to facilitate the settlement down to a straight grade.

 

[cvg]

using flexible waterstops at each joint you could accommodate some differential settlement without damaging the joints or causing leakage. Keeping water from exfiltrating through the joints will also help to reduce settlement. If joints aren't flexible, the box will need to span any subsided areas and you may get some cracking. Over-excavate the subgrade to remove any soft or collapsible soils and replace with good, granular bedding material prior to constructing the box.

 

[mudman54]

i agree with wiktor. the differential settlement criteria should be based on the distortion that the box can handle. if it is a box, then you not only have to worry about the longitudinal settlement profile, but the racking that can occur in the transverse direction.

 

[dicksewerrat]

Is this open cut or a jacking project?

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com