XS with Lid – very high water surface profile?

[Igloo_79]

I am modelling box culverts of 30-40m length on a concrete channel which are essentially long bridge decks over the channel (little or no lateral constriction on the channel width – see XS plot below). I attempted to model them as 2 cross sections ‘with lids’ (inc Priesmmann’s Slots), however, the water levels have gone crazy – see WS profile > 50m below compared to those when modelled as a culvert (red line).

The XS with Lids option seems like a useful tool since some of the culvert inlets and outlets vary in shape, or there are changes in profile within the culverts which cannot be modelled using the standard Culvert option. I also have a 500m culvert to model which will be v tricky without this tool.

Has anyone had similar results, or can suggest solutions? Thanks.

[Anonymous]

Could you help me with how to add lid in my culvert
I have a culvert need to design with two different slope 5% and 7%. My beginning culvert station is 549 519 and 410
549 to 519 station is 5% slope. How can I create a culvert with two different slope . Could you give me some detail idea I am new in hecras or could you give me details how you added lid in which station and how can we connect culvert in series?

[Igloo_79]

Hi – first you need to set up your model with standard open channel cross sections, including the internal XS of the culvert. To add XS with lids, select the XS at the upstream face of the culvert:

Open the geometry editor > Options > Add a Lid to XS > enter data for high and low chord plus tick ‘add Preissman slot’.

You will need to repeat this for every internal XS of the culvert up to and including the DS face. Don’t forget to adjust expansion/contraction coefficients too.

My understanding is that XS with Lids is designed for modelling long culverts with internal changes in XS geometry. I think that the high WSE in my previous posts were related to model instability, which has subsequently been resolved.

Good luck!

[sthsajan]

I made a series of culvert with lidded cross section in between two culvert.
This culvert is proposed to extend the 25 ft in upstream so I do not have proposed contour or cross section of 25 ft upstream side
I created a culvert I have a issue regarding the cross section how water flow in culvert and lidded cross section. is there any way that I can control water flow only in the perimeter of lidded cross section same like in culvert so that that I can get the exact water elevation in the lidded cross section. my water is flowing outside of lidded cross section

[Igloo_79]

To restrict flow to within the culvert like XS 516, you need to extend the geometry of the ‘lid’ to the left and right so that it covers the XS width and is greyed out like in 516.

[sthsajan]

my culvert opening is just 6 feet so I wanna restrict my flow with in 6 foot in the lidded cross section so the water level can raise. it looks like I have wide opening in lidded cross section since I do not have the proposed contour in that section I am creating the lidded cross section in the existing ground but wanna restrict the flow with in 6 foot of the opening but the opening looks more than 10 ft

[Igloo_79]

You need to replicate the high/low chord data in the XS with Lids editor so that is looks similar to XS 516, with a rectangular bridge opening rather than a deck across the channel.

[Anonymous]

Hi, I have same problem, model instability with lid and priesmann slot, how can i resolve the problem? Can I have some suggestion from you?
Thank you

[Igloo_79]

I think they are likely to be related to instability issues of the model in general. Sorry I cannot be more specific!

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