Ditch¶

Use this dialog to describe a ditch using the parametric method.

Where can I find the dialog?¶

In the toolbox, select SFI Properties... and then Ditch.

Overview¶

You can construct manholes and pipes directly in the chain data, as described in the section on Water and Sewer Design, or transfer points and lines from the application layer to the chain data, as described in the section Documentation of Quantities in Ditches.

The parameters in this dialog, together with the data types in the chain data, are used by the program to automatically build the ditch. The data types in the chain data, or any extra lines, provide the 3D geometry for manholes and pipes, provided that the necessary key information such as pipe dimension and manhole dimension is entered.

There are two main scenarios:

Ditch as a separate SFI model
In this case, you must select a pipe as the master (check CL) in the chain data, so that this becomes the centerline of the SFI model.
Road/tunnel and ditch in the same SFI model
In this case, you should not select a pipe as the master in the chain data, but use the option Ditch centerline offset from main centerline, as described below.

For the ditch, you must select several parameters that control the design.

Generated Layers¶

The following layers are created:

Layer 45: Ditch parametric walls
Layer 46: Ditch parametric foundation
Layer 47: Ditch parametric bedding

Prerequisites

Automatic ditch construction requires that the SFI model contains cross-sections. If you edit the geometry of the pipes, you must generate new cross-sections to capture the changes. To obtain a correct model, there must be cross-sections at all break points.

There is no separate preview window in this dialog (the ditch is built when you click OK), but in the cross-section editor, you get a preview directly in the cross-section. Here, you can zoom and, for example, measure distances. Material types are also updated when editing in the table. You can select which profile you want to view.

Parameters for Layer 45: Ditch Parametric Walls¶

Start by selecting one of the following design types:

Normal¶

Design type Normal

For this type, you specify a slope for the ditch wall in soil.

Shallow/Deep with Two Surfaces¶

A = Limit shallow/deep ditch

For this type, you specify two slopes for the ditch wall in soil. In addition, you must specify the threshold value for when the shallow slope and deep slope should be used.

Shallow/Deep from Wall Heights¶

For this type, you specify two slopes for the ditch wall in soil, but only one is used depending on the ditch depth. The vertical wall height is used as the control. You can choose to treat each side separately, so that in sloping terrain you can have different slopes on the left and right sides.

A = Limit shallow/deep ditch

Shallow/Deep from Ditch Center¶

For this type, you specify two slopes for the ditch wall in soil, but only one is used depending on the ditch depth. The height at the ditch center is used as the control.

A = Ditch center, B = Trench

Terraced Ditch Bottom¶

You can have the program terrace the ditch bottom. The only parameter you specify is the slope angle between the different levels.

Example of terraced ditch bottom

In cross-sections with manholes, the ditch bottom is not terraced.

Extension for Manholes¶

Sometimes you are paid per manhole, and then the ditch should only follow the pipes. This is handled with the checkbox Consider manholes.

Example where manholes are considered

You can also trim the ditch against a layer in the SFI model, for example, an advanced cut for the trench. The cutting surfaces are defined to trim against the strata (soil and rock), but you can override this with Trim. With Trim, you can make the cutting surfaces trim against the cut layer, even if the cut layer, for example, is above the stratum.

Minimum Distance Requirements¶

The figure shows distances relative to pipe center

You can specify minimum distance requirements:

Distance from pipe to ditch wall
Distance from top pipe to bedding
Thickness of foundation
Minimum ditch width

The minimum distances to the ditch wall depend on the pipe dimension. You can set up or change the requirements in the table and optionally save them in your own templates for later use.

Example

Pipe dimension 0.100 gives distance 0.200 (less than the first given value)
Pipe dimension 0.225 gives distance 0.250
Pipe dimension 0.349 gives distance 0.250
Pipe dimension 0.350 gives distance 0.350
Pipe dimension 1.500 gives distance 0.500 (higher than the last given value)

You can also change the position that the minimum distances refer to with the option Pipe position for calculation, for example, center or bottom of the pipe.

You can select different pipe positions for calculation

Stop Ditch in Undefined Areas¶

Checkbox for undefined areas, i.e., areas in the ditch without pipes. The checkbox is not checked by default. The ditch will be interpolated in undefined areas.

Parameters for Layer 46: Ditch Parametric Foundation¶

The requirements for foundation thickness are also specified with a table

The lowest point on the lowest pipe is used to determine whether you are in soil or rock.

When the section has no pipes, the lowest manhole is used. In these cases, the value for dimension 0.0 is used. When the section has both pipes and manholes, the lowest value is used, and if they are equal, the pipe is used.

For old SFI models, a line will be created in the table, for example, dim: 0.0, soil thickness: 0.15, rock thickness: 0.15, from a single value.

Parameters for Layer 47: Ditch Parametric Bedding¶

Next, you must select bedding methods. You can have different bedding methods in soil and rock, and you can choose between the following designs:

Horizontal
Follow pipe horizontally
Follow pipe with slope
Follow pipe horizontally, the two uppermost
Follow pipe horizontally, no channels
Follow pipe with slope, no channels

Bedding Methods¶

The bedding methods are best illustrated with some figures:

Horizontal

Follow pipe horizontally

Follow pipe with slope

Follow pipe horizontally, the two uppermost

Follow pipe horizontally, no channels

Follow pipe with slope, no channels

Ditch Centerline Offset from Main Centerline¶

In road models, you can use an extra line as an offset line when building the ditch surfaces. This is especially relevant in tunnels, where you want the ditch to have the same chainage numbers as the road.

You can choose between:

An extra line automatically created from the data type in the chain data
Any existing extra line

For option 1, the program calculates an extra line for the data type you select. This line can also be extended slightly, so you include manholes at the start and end. The extra line is updated automatically if you edit the data type in the chain data.

For option 2, you are responsible for updating the extra line. This extra line is not updated automatically if you edit data types in the chain data.

Important

Be aware that all profile numbers and slopes will be according to the main centerline. This can lead to errors or scaled slopes if the offset line deviates significantly in angle from the main centerline.

Using Surface Tables (Manual Method)¶

In earlier versions of the program, we used surface tables (manual method) for roads to describe ditches.

You can still use surface tables, for example, in cases where the automation fails and you need to make manual adjustments.

With the button Select layers to convert to surface tables (manual method), you can transfer the parametrically defined layers to surface tables.

Layers described with surface tables will take precedence over parametric ditch descriptions. Note that you can have combined ditch construction, where some layers are built with surface tables and others with parametric descriptions. The horizontal list includes, among other things, a column with the calculation method, giving you an overview of this.