6" PVC sch 40 or HDPE N-12 can carry more weight?

[JimS]

Needing to put a small culvert under a drive and don't have a lot of depth to work with. I am going to try for 8" of cover. It's a private drive but for construction will have some concrete trucks on it. Any idea if PVC sch 40 or double wall HDPE is stronger? Any suggestions on bedding material? Sand?

 

[RNeumann]

HDPE can flex more where PVC will tend to crack. As the pipe is pressed from above the sides will try to push out making the pipe egg shaped. To prevent this use tighter packing material (not sand) or concrete. 8” over a 6” pipe should be fine. You could also do 2x 4” pipes.

 

[Streetcar]

Schedule 40 pvc is not designed as culvert. Sdr PVC pipe is designed as culvert

 

[Streetcar]

For shallow culverts I use ductile iron pipe

 

[JimS]

Thinking I will go with 4" pvc. The small sizes of HDPE are hard to find locally although I did find 6". Perhaps 4" HDPE if I can find it. Sch 40 has less overall height due to no corrugations so I can get a little more coverage depth but it's not a huge amount. I can see the flexibility of HDPE being a plus. And the flow will be spread out a bit more with smaller pipes. On the fill if I don't do concrete what is the preferred type fill around it? One of the suppliers stated for the HDPE it should be non-compacting fill. I am guessing that means something like clean gravel? I am looking at installation info now and not familiar with fill classes 1, 2, 3, etc... I can probably put a foot or so between the pipes which seems better than close together.

 

[JimS]

Schedule 40 pvc is not designed as culvert. Sdr PVC pipe is designed as culvert

SDR what number? SDR 35 is considerably thinner than sch 40. A friend in the road business recommended C900 which is even thicker but seems like overkill - perhaps not. I haven't tried to locate some in small sizes.

 

[JimS]

Seems the recommended fill is with minimal fines. I found this spec for class I
ASTM D2321 Soil Class I
Manufactured Aggregates
Crushed rock with angular, fractured particle faces.
100% passing the 1½” sieve
15% or less passing the #4 sieve
25% or less passing the ⅜” sieve
12% or less passing the #200 sieve
Open graded, high permeabilityAASHTO No. 57 stone commonly used

So I should be asking for #57 stone? How about clean 3/4"? Probably more available and I could use the remainder of the load other places - top dress a road where I don't want the larger material.

 

[RickB]

Anything under 12” diameter will be constantly plugged with debris. A well constructed swale will serve you better.

 

[s219]

PVC is brittle (more so in cold weather) and cannot flex much. I would never want to use it as a culvert pipe even if there was enough cover. The reinforced HDPE "dual wall" pipes are very strong and will flex instead of break.

4" pipe is a waste of time as it will plug up and then you'll have a real pain on your hands. I would not go smaller than 8" diameter, and 12-15" is the minimum allowed here.

If done right, the pipe won't be carrying traffic loads, only arch loads from supporting the fill/cover material.

If short on vertical space, you can dig the pipe down if needed -- don't overlook that little trick. A 12-15" pipe dug down 4-5" is still better than a smaller pipe.

 

[fried1765]

PVC is brittle (more so in cold weather) and cannot flex much. I would never want to use it as a culvert pipe even if there was enough cover. The reinforced HDPE "dual wall" pipes are very strong and will flex instead of break.

4" pipe is a waste of time as it will plug up and then you'll have a real pain on your hands. I would not go smaller than 8" diameter, and 12-15" is the minimum allowed here.

If done right, the pipe won't be carrying traffic loads, only arch loads from supporting the fill/cover material.

If short on vertical space, you can dig the pipe down if needed -- don't overlook that little trick. A 12-15" pipe dug down 4-5" is still better than a smaller pipe.

EXACTLY CORRECT!