Support
Topsoil and sanitation in the reinforcement area
Summary
Working with roadbed reinforcements in MDT raises questions about how topsoil and sanitation (the undercut treatment) behave in that area: why topsoil is not drawn at certain stations over a carriageway reinforcement area, why sanitation is applied to the whole section and cannot exclude only the area to be reinforced, and whether sanitation can be defined from a particular vertex of a ditch. This article explains how the program behaves in each case and the documented solutions or limitations.
Applies to
MDT — the documented enquiries do not indicate a version. The embankment sanitation and the exclusion of areas for topsoil are described in the same way in the MDT 26 reference manual.
Templates and roadbeds functions: topsoil and sanitation (undercut) in the reinforcement area.
Symptoms
At certain stations, topsoil is not drawn over a carriageway reinforcement area.
The sanitation (undercut) function is not applied selectively to the reinforcement area alone.
Sanitation cannot be applied from a particular vertex of a ditch.
Cause
Topsoil is set not to be applied between certain codes (in the documented case, between the PV codes of the pavement).
Sanitation is applied to the whole section between the slope contacts on both sides, without distinguishing a particular reinforcement area within that section.
Sanitation is defined parallel to the section itself (the "Selected soil" layer of the roadbed section), so it cannot be tied to a particular vertex of a ditch.
Solution
Case: topsoil is not drawn in a reinforcement area
Topsoil is set not to be applied between certain codes (in the documented case, between the PV codes of the pavement), which is why it is not drawn in that area.
To omit topsoil only in an area under a particular element (for example, under a sidewalk on one side of the alignment), make a code change directly in the corresponding cross section, manually.
Case: sanitation is not applied selectively in the reinforcement area
As implemented, sanitation is applied to the whole section between the slope contacts on both sides, so it does not allow the area to be reinforced to be excluded on its own within the affected section.
This limitation was passed on as a possible improvement. The MDT 26 reference manual still does not include any option to exclude a particular area from the sanitation, unlike topsoil, where regions can indeed be excluded by designating closed polylines.
Case: applying sanitation from a particular vertex of a ditch
It is not possible to define sanitation from the lower vertex of the ditch.
Sanitation is defined parallel to the section itself, within the roadbed section, in the Selected soil layer.
If the sanitation thickness is continuous and fixed across the whole section, enter that value directly in that section.
If the problem persists
If you need to attach several files (the segment and the drawing, for instance) to the same enquiry, compress them beforehand into a single ZIP file.
The support team has videos explaining how to handle topsoil in the cross section; attach your segment when opening the enquiry to get an answer tailored to your case.
If the behaviour of topsoil or sanitation does not suit what you need in your project, contact APLITOP technical support.
Category: Templates and roadbeds · Level: Advanced