how to define pipe crossing

Hello Ammar,

We may need more information on the setup of this. One thing to consider is using a conduit control structure, if the crossing pipe partially blocks flow in the conduit. If that isn't what you are looking, we will need additional information on this.

Regards,

Scott

Thanks Scott,

Actually, the pipe is crossing from the midway(center) of the culvert as shown in the cross-section attached to my last question. if it would cross from the bottom I could use "weir" as a conduit control structure. what can I do in this scenario since it has a clearance of waterway from top and bottom of crossing pipe? please elaborate further.

Hello Ammar,

From the cross-section drawing you shared, it seems the conduit is cradled by some means from the top of the culvert. Is it like a carrying case for the pipe for crossing that section? 

Ammar khan said:

what can I do in this scenario since it has a clearance of waterway from top and bottom of crossing pipe? please elaborate further.

Are the culvert hydraulics going to dictate the hydraulics in this crossing conduit? From your description it seems the invert level of this well above the max allowable HGL in the culvert. Is this correct? What do you mean by "clearance of waterway from top"? Is the conduit getting submerged during high flows through the culvert? 

From what I can understand from your system, the pipe is simply crossing the culvert and if the hydraulics in it are not influenced by the culvert hydraulics you can setup this in SewerGEMS as below;

The above setup assumes that the hydraulics of the pipe and the culvert do not influence / depend on each other.

Let me know if this helps. If not please help us understand what you are trying to model by elaborating on your problem. Maybe provide a detailed schematic / plan view of how this system should work.

Thanks, Yashodhan for your reply.

let me brief you about the existing & proposed situation.

Existing Situation:

In the existing situation, a tributary is falling into the main drain as shown below. There are no restrictions

Proposed Situation:

In this case, the sewer is crossing from the tributary. To accommodate the reduction in the crossectional area of a tributary (due to sewer crossing), we have enhanced the width of a tributary. refer attached image.

The likelihood of submergence of sewer pipe during rainfall event is there . we would like to analyze the impact of crossing sewer on hydraulic behavior.

kindly, provide guidance on how to model this scenario in sewergem.

This seems similar to what I have shown in SewerGEMS. The conduit is simply passing through the culvert but is not influencing the hydraulics of the culvert. The only impact that could be is during larger return periods there could be high flows which could lead to conduit submergence leading to infiltration during those events. 

You can calculate the HGL in the culvert during your higher return events and compare it with the invert location of the conduit to know how much of the conduit is going to be submerged. You can input infiltration rate along the length or surface area of the submerged conduit to account for infiltration flow due to submergence.

However, typically there is space above the culvert for road laying / supporting the bridge deck within which the utilities such as storm drains, sewers, power lines etc. are accommodated. These are hydraulically separate and can be modeled as I have shown above.

Is there not enough thickness available between the deck and the pavement top? Can you divert the sewer where there is enough depth available?