Slip Lining - Culvert Rehab Discussion

[civilman72]

I've tried to search the forum but supisingly haven't found a lot of discussion regarding culvert rehab, at least not the with people's experience of product issues after construction has been completed.

The agency I do engineerng work for is considering slip lining numerous CMPs that are under large fills (>10') and I've been tasked with researching options and costs. The choices are endless, and the products salesmen all proclaim their products work. But considering the lack of history for the majority of these remediation options, it's easy to be skeptical.

I spoke with a local DOT hydraulic engineer who has lots of slip-lining experience. He is having lots of issues with expansion/contraction of the HDPE lining pipes and he's concerned with the long-term integrity of the culvert and surrounding grout. He stated these culverts were connected with the concrete headwalls by removing the outside liner and allowing the concrete to tie-in with the culvert corrugations, which is the method that the manufacturer's rep states stops the culvert from moving. He is now experimenting with allowing the culvert to "float" and not require a tie-in to the headwalls.

I'm in a very cold region of Colorado, so temperature fluctuation is a major design concern (80 deg. (F) in the summer and as cold as -30 deg (F) in the winter).

Anybody have experience with success/failures of culvert rehab projects? Specific discussion of slip lining would be helpful, but I would welcome comments on all types of culvert rehab options. Thanks!

 

[dicksewerrat]

Have you considered CIPP?

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[beej67]

I've seen some CIPP installations down here, but freeze/thaw isn't a huge deal for us. It was expensive, but worked, and in some cases was less expensive than ripping the thing out. Especially in the case of deep pipes.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[coloeng]

I have used CIPP for dam outlets on the Grand Mesa in Colorado (10,500 ft. elev.). It worked well and have had no issues with expansion/contraction, but is probably more expensive than sliplining.

 

[civilman72]

Yep. Definitely have researched CIPP and currently consider it a viable alternative.

It is more expensive than sliplining, particularly at the larger pipe sizes we are dealing with (48"-60"), but still a lot less expensive than open cut or boring in a new pipe.

I have some concerns with the longevity of the resin product... It may hold up and look good over the first 5-10 years, but there has to be some fatigue/breakdown of the product at some point (kind of like asphalt?). Does this fatigue decrease the structural capacity over time? Is there a method to inspect and repair the product or does it require another CIPP liner when it begins to fail?

I know that the HDPE product used in most slip lined culverts generally has a 50 year "life-expectancy" but that doesn't include the grout, which seems to be the bigger issue with current failing installations.

If I consider CIPP, I'm also intrigued by the centrifugal and spray-on products.

Any more input and comments would be appreciated.

 

[SMIAH]

Here in Canada, we do ALOT of culvert sliplining.

Grout (support, pressure, deflection, voids, lifting force, settlement) is an issue but there are special mix easing the installation without decreasing long-term performance.
Hydraulic performance is usually a problem as most culverts are controlled by the entrance geometry (vs manufacturer's rep pretending "increasing the capacity with the manning coefficient").
Mosf ot the HDPE pipe considered are from KWH (Weholite) with threaded joints (under 48'').

As with CIPP, the contractor has to prepare a plan with grout design, mix type, samples and test data (28 day compressive strength).

 

[dicksewerrat]

CIPP is designed for a 50 year life. There is less loss of capacity in the line than with slip lining. There are also some liners coming into the market that are thinner and stronger than the Poly felt and polyester resin commonly used for CIPP. The liners are reinforced with fiberglass.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[civilman72]

SMIAH,

I agree with your statement about the loss of capacity at the entrance. All of the culverts we are repairing are under inlet control, so improved/expanded inlets are being considered. Weholite offers these types of inlets - basically enlarged flared end sections.

While the spec for grout seems to be fairly standard, the long-term integrity of the connection between the grout and pipe seems to be a legitimate concern, particularly when the pipe appears to be pulling away from the grout during expansion/contraction of HDPE pipe. Have you observed this kind of movement?

 

[SMIAH]

"convergent" inlets... if you have the room for it (ROW) + they're $ for large diameter. Do you really need it them?

Some design were with both inlet & outlet enlarged sections ... to maximize decreasing velocity at the end of the pipe (I'm not convinced it really works).

IMO, This is a major concern for sliplining.

I remember one culvert with a velocity of 20 fps (increasing rugosity and decreasing the diameter)...
Even tried to decrease the HDPE slope by forcing the upstream HDPE invert to the culvert invert and downstream HDPE crown on the culvert crown.
With anti-seep collars.
But then, what can you do for outlet velocity protection?
I don't like basin/rip rap protection for 20 fps... Concrete slab? (ROW, $ issue).


Grout has to fill the voids and you have to make sure that there won't be air trapped inside.
You will do that by "observation bore tube" on the pipe (minimum one at the entrance and one at the end + intermediary one if the culvert length justify it).
Filling the void from downstream to upstream and then watching close for discrepancy between theorical quantity vs real quantity.
If the pipe floats, the construction method isn't good.
Some contractors use renforcement steel rods placed between the culvert and the HDPE.

I would'nt consider sliplining for a really damaged culvert as this might be a sign of structural problem over the culvert.
Plus, there are some culverts where you can't use sliplining based on increasing velocity + lack of capacity.

 

[civilman72]

Thanks SMIAH - I'm familiar with the grout installation procedures, pipe guides (one contractor here used old guardrail), observation ports, floatation concerns, etc.

So, I'm not too concerned with the grout installation specs but rather I'm trying to figure out if anyone else has witnessed concerns with the HDPE pipe movement after construction and what issues this causes over time. As an example, does it make sense to try to connect the pipe ends with the headwalls or should it be allowed to "float" as discussed above?

With regards to increased velocity and oulet protection, I will probably design a grouted riprap pad. Another option may be articulated concrete blocks.

 

[gbam]

civilman72;
Have you checked with your State DOT Material and/or drainage section. Here our State DOT has a section that evaluates different products prior to acceptance on the DOT's approved products list. Our DOT has used the poly liners for some time and are acceptable to the quirks.

 

[SMIAH]

All the projects that I know of, are from 2006 to now.
So no concerns but... I'm not involved in the inspection (maybe that's why I don't know of any concerns!).

If it don't float during construction will it float ... 28 days after ? Plus there might be a sediment bed forming in the new HDPE pipe preventing it from floating.

Sliplining isn't a durable technique IMO. Decreasing the capacity of a culvert makes sense when you're dealing with overdesign culvert (hard to show) or when reconstruction is nearly impossible or $$$.

 

[cvg]

HDPE elongates as a function of the temperature change and length of the pipe. based on the installation temperature and un-restrained length of the pipe, expansion "delta" may not be the large. it would need to be evaluated case by case.

since culverts joints are generally "soil tight" not "water proof", allowing the pipe to float might be acceptable.

centrifugal shotcrete lining might be a better option

http://www.centripipe.com/site/CentriPipe/tabid/65/Default.aspx

 

[dicksewerrat]

CMP pipe does not have good flow characteristics. Any liner installed will give a better 'Q'. But a CIPP liner will mimic the exiting pipe and give you a mechanical lock inside the old pipe. Also for odd shapes,( arch, ellipse, horseshoe, egg) you will have a higher 'Q' with CIPP than with sliplining.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[civilman72]

gbam: I have checked the DOT Approved Product list and they include slip lining products, CIPP,

But when I discussed this list with the local DOT region hydraulic engineer he said he is hesitant to spec anything besides slip lining and CIPP, but stated that contractors generally did not bid the CIPP options, so he has little hands-on experience. Even though he's currently experiencing issues with previous slip lining projects, I don't think he's any more confident in the other remediation options.

SMIAH: When I used the term "float" it simply means that the new pipe is not connected to the inlet/outlet headwalls; it would still include standard grout installation in the annular space.

"I would'nt consider sliplining for a really damaged culvert as this might be a sign of structural problem over the culvert."
Could you expand on this statement? I thought one of the selling points of slip lining was that the new pipe did not rely on the structural integrity of the existing pipe. I would be more concerned with using CIPP on a pipe that is clearly failing (i.e. sagging, joint displacement, etc.).

cvg: Correct that the amount of displacement from expansion/contraction is directly related the length of pipe. One of these rehab projects is a 380' existing pipe, so movement of will be excessive and is a concern of mine. One of the County Road and Bridge personnel that I work with shared his previous experience with a welded HDPE pipe that he were using a bulldozer to pull through an existing pipe. He left the bulldozer (I think it was a D8) hooked up to the pipe and he claims the bulldozer was pulled more than 2' by the pipe movement overnight. This was late in the fall when temperature can fluctuate as much as 50 degrees in a 24-hour period.

 

[SMIAH]

I have concerns if it's an old corrugated pipe with corrosion and loss of thickness, and if you have a significant grout volume (i.e. depth) over the HDPE.

Long-term durability of the grout and it's ability to support the foundation of buried soil over it.

 

[civilman72]

SMIAH: My understanding is that the compressive strength of the grout is much larger than normal soil, so the structural concerns should be with the pipe only. But maybe I'm missing something?

I didn't finish the list of approved pipe rehab products from the DOT: Slip lining, CIPP, SPR (Sprial-Wound Pipeline Renewal), Centri-Pipe and Permacast (centrifugally cast concrete pipe). As mentioned above, they have a long list of approved products, but generally are only comfortable using slip-lining for their pipe rehab projects.

 

[cvg]

if slip lining is the preferred method, than line it with something other than fused HDPE. Perhaps FRP pipes (such as Hobas) would be a better option. It isn't nearly as sensative to temperature as HDPE.

http://www.hobaspipe.com/case-histories/dot-and-stormwater-drainage/macomb-county-emergency-repair/

 

[dicksewerrat]

CIPP is designed as a 'stand alone' pipe. Not dependent on the 'host' pipe other than to use the existing hole in the ground.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[SMIAH]

You're right civlman72 about compressive strength of the grout alone.

I don't know about HDPE or grout+HDPE (as a combination) structural ability to take mechanical stresses (compression, tension, and shear).

From my understanding, HDPE pipe has little inherent strength and it's overall stability depends on a properly installed and compacted embedding material + around the pipe.
What if the culvert is already damaged and under a large fill?

Deflection of HDPE is a common issue too, isn't?