Vaidas
It is a little difficult for me to visualize this without the data for the project - the uncompacted PCS surface is designed to compute a Paving surface that is variable height based on the thickness of asphalt required after compaction - so you have the Milled Surface and the Design Surface and it will compute the Pave surface based on a compaction factor that you enter that takes into account the thickness of the asphalt required at any location - so if the Design - Mill = 10cm and you use a 20% factor then the Paving surface computed would be 12cm thick at that location. Where the Design - Mill = 8 cm then the paving surface would be 9.6 cm etc. this creates a non uniform paving surface which will look awful when laid by the paver, but if your compaction factor is correct should look perfect after rolling.
From what I can read into your requirement here - it seems like you have the following
1) A Final Design Surface Model that you have to create
2) An existing pavement surface model that needs to be milled by different amounts in different areas
2) Some parameters that define the amount of milling that needs to be done in different areas of the existing surface to create a Milled Surface model
If you have the areas of milling defined - then you can do the following
1) Draw the milling area boundaries as 2D polylines (closed area polygons)
2) Use the Change Elevation command to change the elevation of the 2D lines to 3D by using the From Surface option and selecting the existing surface model as the reference. This will "drape" them onto the surface model
3) Change the properties of those lines from Sharp to Sharp and Texture Boundary
4) Add the lines as surface members to the existing surface model
5) Create a Material in the MSI Manager called eg Mill Cut. Make a Site Improvement called 2cm Mill Cut that has a single layer of Mill Cut Material 2cm thick
6) Use the Create Site Improvement Command to place a Site Improvement (the 2cm Mill Cut) in the areas where you need to mill off 2cm.
7) Now you can use the Create Subgrade Surface command to create a subgrade adjusted surface from the Existing Surface Model to "Bottom of Engineered Materials" or Bottom of 2cm Mill Cut layer (either works) and that will drop out the 2cm mill off in the areas for you.
8) For the Fill - I am not sure exactly what you mean there - but you have to fill to the Design Elevation from whatever the Milled Surface Elevation will be by variable depths of Asphalt as defined by the difference between the Design and Mill Surface model - but you have stated that it is in 2 layers a 5 cm layer and a 3cm layer - so you will need a design surface for each of those two surfaces that you are trying to create. Once you have those you have the 5cm Layer Design and the Mill Surface model - so you can use the Uncompacted PCS surface function to compute the 5CM Paving Surface model. Then you have the 3cm Layer Design and the 5cm Layer Design and this should be a uniform thickness layer I would have thought because the variable thickness layer should be the 5cm layer.
If the Fill Areas are prior to the 5cm layer being laid and vary from 0 - 8cm thick - how is that defined on the drawing / cad - are they shown as thickness contours or something like that or just areas (polygons) showing different depths of extra asphalt - how that is defined on the plans will dictate how that gets added to the Mill Surface that you create using the subgrade adjustments above
So I would
1) Take my Existing road surface and apply the Mill Areas first and create the Mill surface
2) To the Mill Surface model - I would add in the Fill area information to create a Base Surface for re-construction
3) I would assume that the Base Surface should be a uniform 5cm thickness below the 5cm Asphalt layer design - if that is not the case then it is the 5cm layer of asphalt that will take up the variable thickness so that the 3cm layer is a uniform mat thickness I would have thought?
4) So if the 5cm layer is not a uniform thickness, then I would use create uncompacted PCS srface using the 5cm Design and the Base Surface Model with the compaction factor to compute the uncompacted PCS surface for the 5cm asphalt layer. If you just want to thicken a uniform 5cm layer to allow for 20% compaction etc. then you can use this command also or you can simply raise the thickness by 20% to eg 6cm thick to create that.
5) The 3cm layer will be the same approach as the 5cm layer - but I would assume that is a uniform thickness - so making that 3.6cm (20% compaction) is likely all you need to do
If it is the base surface that you want to compute the variable thickness on - then you have your Mill Surface (combination of Mill Areas and Existing) and you have your Base Surface (combination of Mill and Existing and Fill Areas) so you can run the uncompacted PCS surface on those to compute the expanded fill areas - where the mill = mill you will have 0 thickness so that will remain the same.
If you can share the data I can assist you further, however I hope that this gives you the path to follow here
Let me know if I can help further
Alan