In ordinary road pavement, the different layers are normally laid out parallel to the Road Pavement Description. With the rehabilitation function, the lower edge of the designated road pavement can be forced to meet with the top surface of the existing road.
This assimilation will only happen at each cross-section and not along the length of the road alignment.
The starting point for the assimilation is the terrain top surface, where an existing road will be defined based on illustration codes for the right and left road edges.
Against the surface delimited by the road edges, it is possible to have the road pavement assimilated.
Refer to the topic Rehabilitation - Examples for graphical illustrations.
Run the function from the following location of the floating window 'Road Model':
MOUS_ICO Toolbar: Not available from Toolbar
MOUS_ICO Menu: Data > Road Pavement > Rehabilitation
The dialog box Rehabilitation (shown below) will pop up.
Note: For the Rehabilitation to work the alignments used for the rehabilitation has to be added as Illustration Objects to the road model.
Rehabilitation can be defined for a given section by entering values for the From and To stations.
Reduction of effective width for existing road
Assimilation should be carried out between the left and right edges of an existing road.
To define other delimiting points, define a reduction of the effective width.
This might be applicable if the fill-out on the edges is of such poor quality that a full road pavement should nevertheless be built there.
The distance within the edges of the existing road at which assimilation has to begin should be defined as a reduction of the effective width.
The width will be defined in meters and can be different on the left and right sides.
The pavement thicknesses found under road surface 1.01 are added here.
If the height difference between the new and existing road is less than this value, a full road pavement will be laid out, without assimilation.
The layer depths defined in the Road Pavement Description will be used.
The value can be within the total road pavement thickness.
For several section descriptions, SECTION FROM will be used to look for the road pavement description within which this profile is situated.
Maximum values for the thickness of the individual layers should be defined as somewhat greater than the normal thickness (cannot be defined for sub-base 2).
The road pavement layers will be laid out until the limit for maximum layer thickness is reached.
When the limit is exceeded, the normal thickness for the layer will be used and the assimilation will now occur in the layer below.
The minimum thickness for each individual layer need not be defined. This is equal to the difference between the maximum thickness and the normal thickness for the overlying layer.
Use for rehab
Wearing course will always be included when doing rehabilitation as it is the uppermost layer and because a perfect match between the new and old road will never be 100% identical.
However, if you would like to always include any of the lower layers with at least the minimum thickness then check the box for Use for rehab. All layers above will be added with standard pavement thickness from the normal pavement description.
Min. width standard pavement
The width here is defining the minimum width of the roadbed for the new pavement outside of the road edges. If the rehabilitation function detects that this width is too narrow it will extend the new pavement into the old/existing pavement.
The use for this function is to make a design that will meet the construction equipment on sight for a more effective build, i.e. not making too small strips of new pavement not suited for the equipment the contractor has.
Min. width reduced pavement
The width here is defining the minimum width for the old/existing pavement at the level of the roadbed of the new pavement.
The use for this function is to set a minimum width of the existing road before the existing road is considered to small to keep. When the width of the existing pavement gets too small it will remove it completely and replace it with new pavement in the full cross-section.
A fixed depth to remove material in the existing pavement before adding the new design. Normally 4 cm for the existing wearing course is removed so that the new wearing course can be added in its place. Alternatively, no fixed scarifying is added and the user could place the new road some centimeters above the existing road instead.
In some cases, additional scarifying (removal of the existing pavement) could be done to save the existing pavement and not replacing it with new pavement where it is not needed. Examples of this could be in situations where we know the existing road has had multiple layers of wearing courses added as part of the maintenance of the topmost surface. To keep most of the existing pavement at the end solution additional scarifying will remove material where the new road surface dips to low.
Road edges defined by
Use feature type to pick between line objects included in the tasks illustration objects as reference for the left and right road edges for the rehab function.
Use alignment to pick line tasks from the model to use as left and right road edges for the rehabilitation function.
Existing road edge
Pick the edge lines for the rehabilitation function.
Extra distance (+/-)
The extra distance is added as positive (+) when the new pavement should be placed closer to the reference alignment of the new road model. This is a horizontal displacement.
Use negative (-) values to move the start of the new pavement further away from the reference alignment of the new road model. This is a horizontal displacement.
Side slope left/right
This is the slope of the transition from the new pavement to the existing pavement.
Today constantly increasing shares of road budget go on improvements and alterations to existing roads and streets. One of our aims is to utilize the qualities of existing roads as far as possible. In many cases, it would be desirable to lay a new road on top of an existing one without having to cut down into it.
In the rehabilitation of existing roads, the road pavement thickness can vary within the given minimum and maximum limits. The assimilation can occur in all road pavement layers except for reinforcement layer 2. Reinforcement layer 2 is always laid out at its full depth, whether or not it is assimilated. In this case, the overlying layers will be assimilated to this adjusted top surface. Which road pavement layers the assimilation is to be carried out on is dependent on the height discrepancy between the new and the existing road top surface. Layers on top of the layer in which the assimilation is to occur will be laid out at the normal thickness (from the road pavement description). Layers that are described in the road pavement description but which will theoretically be situated below the layer currently being adapted will not be laid out.
The figure below shows examples of rehabilitation of existing roads. In the lower profile, a reinforcement layer 2 has also been inserted.
As a rule, the existing road and the new road will have different cross-sections. On assimilation, one of the road pavement layers will be given a variable thickness inside one part of the profile. The width of the assimilation interval will depend on how the height difference between the two roads varies across the profile and the given maximum depths of the layers. In the same cross-section, assimilation can be done in several road pavement layers, such as both the load-bearing layers and the reinforcement layers. Layers, which for the moment will not be assimilated, are laid out with their normal thickness based on standard road pavement thickness. This will be a layer lying on top of the layer being assimilated. Layers that are defined, but which theoretically are to be located below the layer being assimilated, will not be laid out. It is possible to have two assimilation intervals per layer across the cross-section (the roads will also be built).
The next figures show the principle of reducing effective width and rehabilitation of existing roads. The figures illustrate the reduction of effective width on existing roads, minimum road pavement thickness, and maximum thickness, in assimilation, for every individual layer. Since the effective width reduction on the left side is given in the top figure, a normal road pavement is laid out over this width. If the effective width reduction in this example were not used, the normal road pavement would not be laid out before the maximum thickness of reinforcement layer 1 was exceeded (pt. A).