Fixing culvert end settlement

[Erdbau]

I have a culvert that drains under a roadway embankment. The culvert inlet (15-foot section of 16-inch RCCP) has settled about 6 inches at the inlet and is now sloped in the opposite direction (away from the embankment, so water pools around the inlet). The downstream side has not settled. Does anyone have any suggestions for resetting the slope of the pipe without excavating and resetting?

 

[Ryb01]

Could I assume that this culvert is now under a freshly paved road?

I have heard about a type of technology where concrete is pumped under a sidewalk or/ slab on grade to lift and support a structure to a required elevation.... you may be able to take a look into something like this. Unfortuneately, I do not have a contact. If you have a paved suyrface over top of this culvert, it will likely crack if you start to lift the pipe.

Another option to look at, depending on conveyance requirements, may be to look at lining the pipe with a steel liner.

Could you line the inlet with rap-rap to minimize the pooling? Does the settling have a big impact on the overall conveyance and headwater elevation of the culvert?

 

[Erdbau]

Yes, the technology you mentioned is called slab jacking or mud jacking, but I don't think it's applicable in this case (1) because the end that needs to be jacked is at the edge of the embankment, so I can't see how any pressure can be developed, and (2) I'm not sure how to control the lifting to make a slope (i.e. the whole section rising and ruining the downstream joint). Plus, as you mentioned, the cracking problem; sidewalk and road approximately 4 feet above.

I like the steel liner idea. I'll have to check the geometry to see how much smaller that liner will be than the original culvert.

 

[emmgjld]

A 'cousin' to slab jacking is Compaction Grouting. This involves drilling into the soils with a small diameter pipe casing and then pumping a grout in, thus 'compacting' the lower soils. The casing is withdrawn a little and more grout is pumped.

This method can also be used to raise the ground surface or structure.

 

[Erdbau]

Even with compaction grouting, though, what is preventing the grout from blowing out from the face of the embankment? I don't see there being enough lateral soil cover to develop enough pressure to lift the culvert. It seems like the grout moving outwards to the face of the embankment is the path of least resistance, as opposed to pushing the culvert upwards. Am I seeing this correctly?

 

[cvg]

place a temporary berm at the end of the pipe. mud jack and monitor the pavement above closely as well as the pipe joint. remove the berm once you have it lifted.

 

[emmgjld]

I don't know your circumstances, so I am only giving rough thoughts. Actually quite unorganized this Friday afternoon.

When I recommend Compaction Grouting for lifting near surface objects, I usually assume the grouting will begin at least 10' below the settled structure. The grout is VERY stiff and the crew had better have 'the touch'.

I just throw it out as a possibility.
Sewer lines have been raised or straightened.
Sewer lines have also been collapsed.

 

[Erdbau]

Emmgjld, your suggestions are definitely appreciated. Cvg's berm idea speaks to the lateral confinement issue. I'll definitely have to investigate further.

 

[dicksewerrat]

Can you jack a 36 inch casing around the pipe past the joint that has come apart? Clear all the soil out, raise the pipe and backgrout the pipe to casing space?

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com