Hydraulic Design - Linear Devices

According to the DNIT drainage manual (IPR 724), culverts can be sized like:

• Channels
• Weirs
• Orifices
• Bureau of Public Roads - NodesA Circular No. 5 - entry or exit control

The choice of regime to adopt depends on the possibility of the work being able or not to work with hydraulic load upstream, which could cause the overflow of the watercourse causing damage to embankments and pavements and flooding upstream from the manhole.

If it is not possible to load upstream, the culvert must work free as a channel.

On the other hand, if the rise in the water level upstream does not pose any risk to the road body, or to third parties, the culvert can be dimensioned as an orifice, respecting, evidently, the quota of the maximum water level upstream.

For culverts working hydraulically as channels, the adopted methodology is referring to flow in critical regime, based on the minimum specific energy equal to the manhole height.

For culverts with upstream load, the flow is considered as a channel in uniform movement, to the full section, without internal pressure.

In addition to these procedures, it is recommended to use the alternative method of "Circular nº 5 of the Bureau of Public Roads - NodesA", based on laboratory tests and field observations.

This methodology applies to both alternatives, i.e. for culverts working with or without hydraulic load, and is fundamentally based on researching the water level to be upstream and downstream of the work.

According to ISF 210 (Railway Services Instruction):

1. it is not allowed to adopt solutions that accumulate water above the design grade line
2. Designing with free board (channel) with discharge calculated for TR=25 years
3. Verification of flow for discharge calculated for TR=50 years, with maximum overelevation of 1.0 meter
4. Concrete pipe: 1.0 m ≤ DN≤ 1.2 m armed
5. Corrugated steel pipe DN ≥ 1.2 m
6. Cellular Gallery, height ≥ 2.0 m and width ≥ 1.5 m
7. Minimum speed: 0.75 m/s
8. Maximum speed (Vmax): 4.5 m/s
9. Minimum cover: 1.0 m, measured on the earthwork platform
10. Power sink whenever V > Vmax
11. Use the same types of road culverts, as long as they are verified: resistance, deformation and stability, foreseeing rail loading of the TB 360 train.

The following methodology is used to calculate the flow rate in the pipe (Qesc):

• Drainage Network
  • Vazão Superficial (Qsup, Double) - portion of flow generated superficially
    • F - is the Fantoli coefficient
    • SCXA - sum of the coefficient C multiplied by the contribution area of the mullion structures
    • CR - is the delay coefficient
    • I - is the precipitation evaluated by the rainfall equation a> for the characteristics of this Catchment
  • Sliding Flow (Qesc, Double)
    Qesc = Qmon + Qsup
    Where:
    • Qmon - is the sum of the direct point flows in the structures upstream of the pipe
    • Qsup - portion of flow generated superficially
  • Flow speed (Vesc, Double)
    Vesc = Qesc / Am
    Where:
    • Qesc - Flow flowing in the pipe
    • Am - Section wet area
  • Travel Time (TP, Double)
    TP = Length2D / Vesc
    Where:
    • Length2D - length in plan of the tube
• Sewer Network
  1. Infiltration Rate (TInfp, Double) - Sum of the infiltration rates of the areas connected to the pipe
     Tinfp = Sum(Zone.TInf)
  2. User Contribution Rate (TUser, Double) - Sum of calculated contribution rates in zones associated with the tube
     TUSer = Sum(Zone.Tx)
     Where Tx is Ti at the beginning of the project and Tf at the end of the project
  3. Upstream Flow (QMon, Double) - Accumulated flow upstream of the stretch
     QMon = pvm.CTop + Summation(pvm.TubosEntrando.QCalc)
  4. Infiltration in the Section (QInf, Double) - Flow by infiltration in the current section
     QInf = TInfp * L Where L is the 2D length of the tube
  5. Contribution on Stretch (QUser, Double) - Flow generated by users in the current stretch
     Quser = TUser * ExtFic
     Where ExtFic - dummy pipe extension
  6. Calculated Flow (Qcalc, Double) - Calculated flow for the stretch
     Qcalc = QMon + QUser + QInf
  7. Flow flowing (Qesc, Double)
     Qesc = Math.Max(Qcalc, net.Qmin)
     Where rede.Qmin - minimum flow to be considered in the pipe

To access these properties, use the Properties Tab, select the linear gravity device and click the icon:

• to edit the dimensioning data
• to edit the verification data