(Computer)
(OP)
11 Dec 06 23:36 Hello All and sorry if this is a redundant question. I am the owner of a property in Northern Calif south of Red Bluff,CA. I want to put a culvert in to access the property from the asphalt county road. I was looking to put a steel 30" culvert which has 34" from the flow line to grade. In the near future I am looking to build a ICF concrete house and need some advice on what to do so this culvert will support the weight. Steel or black plastic ? The county permit says steel or black plastic no concrete. Any ideas or recommendation would be appreciated. )
Thanks once again and sorry about the redundant question
Pulling out hair (Boczech)
(Civil/Environmental)
12 Dec 06 11:26Is there a reason you're using a 30" culvert? Steel and Plastic Pipe get their structural strength from the bedding type and material. 12" of bedding above the pipe is usually standard.
(Computer)
(OP)
13 Dec 06 01:29Hello bpattengale,Thanks for your reply!!) The reason for the 30" culvert is the recommendation from the county on the encroachment permit. The area has alot of water draining through my property and hence the larger culvert. I was looking to get at least 12" of bedding over the culvert to support heavy loads by concrete trucks in the future. Any advice would be appreciated.
(Structural)
13 Dec 06 08:58Two each of 24 inch diameter will take a little more flow than one 30 inch diameter with the additional 6 inches of cover at the same flowline elevation.
(Computer)
(OP)
13 Dec 06 13:34Hello civilperson,
I left that out but I am looking to put two each 30 inch diameter culverts with 36" flare ends (skirts) in the ditch.
(Structural)
13 Dec 06 14:37Elliptical concrete pipe has equivalent flow characteristics to a circular pipe with less height. Thus two elliptical pipes in the same trench gives increased cover. The class of bedding is also instrumental in raising the strength of the pipe for imposed vertical loads. The maximum strength would come from lean concrete backfill or 100 psi flowable fill backfill. The Flared End Sections have the same diameter name as the through pipe they connect to, (even though the width increases).
(Civil/Environmental)
8 Jan 07 07:29The capacity of a 30-inch circular pipe is roughly equivlent to a 35"x24" corrugated metal pipe arch. This would afford you an extra 6-inches of cover. You can also order the end sections for these.
(Geotechnical)
9 Jan 07 19:41Why "no concrete"? You can get varying strength concrete pipes. The supplier can tell you the wheel load capabilities vs cover. Some types can take a load directly on the pipe.
Another option is to place a reinforced concerete pavement slab over this area. A structural engineer can design this to spread out the pressures to tolerable levels.
Then another option with this, you can use the "imperfect ditch" method first recommended by an old Iowa prof., named "Spangler". Before placing the slab spanning the pipes, you add a compressible material as cover over the pipes, such as corn stalks, sawdust, leaves, etc. This mainly is used where the pipe is already in and you are adding more fill, bigger loads, etc. It works.
(Civil/Environmental)
12 Jan 07 14:04Squash pipe (elliptical or arch) does carry about twice the flow as an equivalent rise pipe. In addition, it carries about the same as the source pipe - e.g. 35" x 24" was a 30" round. The reason is that although the area over circumference is slightly smaller, the flow is lower - those two factors average out.
(Civil/Environmental)
12 Jan 07 14:17This is pretty late but,
I like a corrugated black plastic with crushed (angular) 3/4" rock up to the springline (halfway) just make sure you flush and compact it.
This may still help,
Get the concrete trucks to go slow, one of the biggest impacts is a bumping truck. At my house, I have a turn that slows the traffic so running concrete and gravel loadded trucks with only 8" to 12" (different sides of the pipe) for a HDPE 24" pipe has shown no impact. Also make sure the approach and exit remain smooth and no source of pumps appear.
(Civil/Environmental)
12 Jan 07 14:21Compact 3/4" rock?
(Civil/Environmental)
19 Jan 07 09:07Smash into native, push it under the pipe until it won't go. 3/4 won't flow under the pipe and you really need to work at it until you get to the springline.
(Civil/Environmental)
19 Jan 07 10:45slurry / flowable fill is better, however plastic pipe will float so it needs to be anchored down
(Civil/Environmental)
19 Jan 07 15:15It has been a little, but I thought a benefit to HDPE was that it moves with your soil. Seems that with bedding only to the springline you would want bedding that deforms to relieve some pressure?
(Civil/Environmental)
19 Jan 07 15:29I agree some pipe flexibility/ductility in underground joints and pipe is probably good; however, it appears too much flexing might not be too good in some cases for at least some pavements above same (see the plight of the homeowner C1323, who chimed in in the latter part of thread http://www.eng-tips.com/viewthread.cfm?qid=155551&page=1 below)
(Civil/Environmental)
18 Feb 07 20:30The question here is what type of load rating are you trying to achieve? HDPE pipe is very strong if placed properly with proper bedding and is less expensive that steel pipe. Cover and bedding of either pipe will be very important in this case. Using smaller diameter pipe like (2) 24" instead of one 30" is better for distrubuting loads.
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