Ditch Design

General

Ditch Design is the calculation of the surfaces in surface group 4.XX connecting the shoulder to the terrain surface. In the Road Design module, you can select between different methods to perform this calculation.

1. Normal Ditch

2. Advanced Ditch:

   • Absolute method

   • Relative to Vertical Alignment method

   • Relative to the Planum method

   • Relative to the Terrain method

   • Minimum depth

Normal Ditch

Normal ditch design can be done from any of the following:

1. Defining the ditch details using Simple Road Description and later modifying the same using the dialog box Road Surfaces (if modifications are necessary).

2. Defining the ditch details using Advanced Road Description and later modifying the same using the dialog box Road Surfaces (if modifications are necessary).

3. Defining the details directly in the dialog box Road Surfaces, by inserting/selecting one or more surfaces of the surface group Ditch.

When a surface in the surface group (+/-4) is shown for the first time it is a Normal surface.

• This means that the surface is calculated using width/slope.

• The section, width, and slope are to be defined using any of the above three ways.

• Choosing the method Normal and if a ditch has to be calculated in fill (embankment) also, define the start and end stations of the embankment ditch in the dialog box Embankment Ditch.

• When the values in the dialog box Road Surfaces are modified, click the button Apply and calculate the cross-sections.

• Ditch surfaces (+/- 4.XX) of the road models calculated in former versions of Road Design, in which the special functions were not available will be of type Normal.

Advanced Ditch

Advanced Ditch design can be carried out using any of the following ways:

1. Defining the ditch details using Simple Road Description and later modifying the same for advanced design using the button Advanced of the dialog box Road Surfaces.

2. Defining the ditch details using Advanced Road Description and later modifying the same for advanced design using the button Advanced of the dialog box Road Surfaces.

3. Defining the details directly in the dialog box Road Surfaces, by inserting/selecting one or more surfaces of the surface group Ditch and using the button Advanced.

In the above three procedures, in order to carry out advanced ditch design, one of the +/-4.XX surfaces are being changed from Normal to Advanced by pressing the button Advanced of the dialog box Road Surfaces.

• The button Advanced is available only when one of the ditch (+/-4.XX) surfaces is active in the Road Surfaces dialog.

• After changing from Normal to Advanced, the values Width and Slope are still available, and it is not possible to design an advanced ditch unless the values in the column Width are deleted.

  1. Absolute

  2. Relative to Vertical Alignment

  3. Relative to Planum

  4. Relative to Terrain

  5. Minimum depth

• In general, grey cells cannot be edited, and white cells can be edited. Once the values in the column Width are deleted, the grey cells turn to white.

• In order to define the values, decide the section (if the sections station(s) are not available in the table, define the section), and delete the values of column Width related to the section, for which advanced ditch design is being designed.

• Define the values in the column of the method to be used, click the button Apply of the dialog box Road Surfaces and calculate the cross-sections.

• In each method, interpolation will be done between the defined values.

• It is not possible to interpolate between calculation methods. Therefore a new method must be preceded by a break.

• If the method has to be changed in one of the lines in the dialog box the present value must be deleted. Then all fields will turn to white ready for defining new values.

• For more details on the above methods, refer to the respective topics.

• Ditch Depth: If Advanced Ditch Design is in use Ditch Depth = Minimum Depth Below Formation (a Cut and Fill Element) cannot be used.

Absolute

Absolute means that the elevation of the advanced surface is given for at least two profiles between two breaks.

• The method is often used for local correction of the result of other methods.

Relative to Vertical Alignment

In the dialog box, the method is called Relative Longitudinal Profile, but the value in the column is the depth below the vertical alignment.

• It is also possible to interpolate between different depths.

Relative to Planum

When Planum is calculated to an intersection with the advanced 4.xx surface, this method may be used.

The value defined is the depth from the end point of the Planum to the bottom of the ditch.

Relative to Terrain

Using this method, a ditch may be calculated in both formations (cut and fill).

• In this method, the design parameter is the depth from the terrain to the bottom of the ditch.

• The width of the advanced 4.xx surface will vary from profile to profile.

• After calculation, the vertical distance from the shoulder to the bottom of the ditch is compared to the value Minimum Depth defined in the dialog box.

• If this value is not reached the ditch will be made deeper to fulfill the requirement for Minimum Depth.

• Minimum Depth can only be given as one value for each interval.

Minimum Depth

It secures a minimum depth on the ditch when using Relative to Terrain. In a cut, the value for Relative to Terrain could result in having no ditch surface and this function secures a minimum depth on the ditch.

Insert Proposal

Use this function when you need different advanced ditch designs in cut and fill.

The function is available via right-clicking on the surface group for Ditch, and is only available when the ditch is in 'Advanced mode'. The dialog box Insert proposal for ditch surfaces will pop up.

The function is used to apply different advanced ditch designs in fill and cut respectively. Instead of entering the different designs in cut and fill manually for multiple ditch surfaces under 4.xx, the function will help the user with this by analyzing the cross-sections to find the sections for where to input the different ditch designs as specified.

Station

Define the section of the road model, for which this function is being adopted.

• Select the radio button All to apply for the entire section.

• Select the radio button From and define the section using the field From and To to adopt this function for the desired section of the road model.

Advanced Ditch Design

Enter the Advanced method to use. See paragraph about Advanced Ditch above.

Other surfaces

Other surfaces of the ditch group can be defined in this table.

• The surface defined in this table will be of Normal Ditch.

Calculate

• Use this button to calculate the surfaces defined cut and fill conditions in the above dialog box.

• The program prompts to overwrite an existing surface description when the button Calculate is activated. Confirming the same and all the profiles will be calculated with an interval of 1.0m.

• The result of this calculation is to divide the entire road model into intervals of cut and fill. For each of these intervals values are written to the surface description dialog box Road Surfaces.

Note: In Insert Proposal cut/fill intervals and depths are calculated using the values of the other Road surfaces. So if any Road surface is changed Insert Proposal must be run again to be updated.