Slipped formed slotted drain.

[wolfhnd]

check out this site.

http://www.aran.com.au/slipform.htm

I have selected this product for draining the pavement of a roadway that is to be widened, curbed, and currently drains to a center ditch (excellent design but I need the space to add 4 new lanes. I have 40 million dollars worth of buildings to leave on the outside so widening on the outside is not an option.). This road has a 0% grade for 1.5 miles. I can't see the contractor getting it flat enough where I would be happy with DI's. Current standard for principal arterials do not allow spread out of the gutter making this the most attractive alternative I can find. If anyone has any ideas on how to calculate the capacity of the formed pipe please post them. Mannings equation is not usable on a completely flat grade and I'm not up to doing a non linear calculation. No one sees a problem with the concept but I would love one of you structural guys to check the need for reinforcing. I talked to a slip form manufacturer and the cost for the form is about $8000. There is no licensing and have decided to design my own shape, a square with a 15" conduit. I'm also interested in what difficulties I may face getting FHWA approval. Any comments and suggestions welcome.

 

[ishvaaag]

Hydraulically it is an open channel, and so it must be treated. You have 0 slope at the surface, yet need not be the case in the pipe. You should provide positive points of discharge along the pipe, at distances that the slope, or in its defect, the difference of level between the accumulated water is at its maximum level and the level to which discharge is warranted is a piezometric differential enough to deal with the tributary storm flow. Making such outlets close will help to keep the diameters as small as the storm flow allows.

Structurally, wheel loads will damage the rims of the slots, so place them outside traffic. Placing reinforcement may be feasible but quite a mess for this system. It is likely that is within the requirements of a drainage of this kind to understand that some small cracks may appear and water flow pass to the ground there. In reality this is much an understanding for too many sewage works. If an agency demands tight waterflow, then the attention and details proper of pressurized pipes need be put in place, and this may make the slot system inadequate out of costly compatibility with well engineered reinforcement.

 

[pba]

Other manufacturers of slot drains give design literature to enable the designer to check capacity. If you contrive to produce a slip formed drain of similar sectional form to one with published data, the drain capacity should be similar.

Other people may be able to give you some manufacturers supplying similar products in your area.

 

[bltseattle]

I recommend something with a larger inlet than the small slot shown in the photos. The small slot inlet will be easily clogged. Consider a trench drain with removable grates instead of a slot drain.

Have you checked out Aco Drain? Our state DOT was willing to accept them for a similar situation as yours (widening within the right of way, 2-ft gutter spread). The company seems to have well developed hydraulic data available, too.

http://www.acousa.com/drain.htm

 

[cvg]

I have used slotted pipe drains (corrugated metal pipe) extensively for airport drainage. These are used on terminal aprons where slopes are flat and aircraft loadings are quite severe. They don't need any slope. I use sections of slotted drain as an inlet and then drop the flow into a larger pipe storm drain. Reinforced concrete encasement is constructed and specified to withstand 200,000 pound proof loads for jet aircraft (MD-80, 737 etc.). This is well in excess of standard highway loads.

 

[ishvaaag]

Of course if you use thick covers you will get strength. Yet maybe for the width of a highway and softness of the ride is better to keep the slots out of the traffic lanes, just my view. Slots in more than being subject to deterioration at the edges and damage the tires will augment the risks to traffic, specially in rains. Planes enjoy the automated control through their aerodynamical controls and directional power, a luxury cars do not have.

 

[wolfhnd]

The design team says no metal pipes and bicycle safe grates. We have a standard for the cmp slotted drain but no structual data. I assume that if the pipe rots the concrete is designed at airports to maintain a conduit.

 

[wolfhnd]

Are we done?