This Tip illustrates how to determine the horizontal and vertical alignment of a road from a survey of the existing existing road’s centerline and road-edges.
Use the Geometry › Point-Point Line function in CAD mode to draw geometry lines on the straight portions of the road centerline. Use the DTM jump “Shift d” key, or the Grab-All snap mode to jump to centerline points.
Select Alignment › Horizontal › Graphical Insert from the ROADS mode. Insert a start PI on the first centerline point using the “Shift d” key. All the PI points will be located at the geometry intersection points, therefore use the “I” key to jump on these geometry intersections. Enter the last PI point the way you entered the start PI.
To calculate the curve radii, use the Alignment › Horizontal › Fit Curve function. Before you use this function, you need to rename one point near the center of each curve with unique names, e.g. “CNTR1”.
Now select Alignment › Horizontal › Fit Curve.
Indicate the curve number and the name of a point on the curve. Press OK.
The curve radius for curve 1 can now be entered into the Horizontal Alignment spreadsheet. Repeat this procedure for all the remaining PI's.
Save the Horizontal data and coordinate the alignment at the desired intervals. Extract cross sections from the ground surface at these intervals.
The vertical alignment needs to be extracted from the ground model, at the centerline of the road. To do this, you need to transfer a point at offset 0 from the ground gross section layer to the Layer 128.
Civil Designer uses Layer 128 as a 'Scratch pad' layer for various calculations. It will expect the vertical alignment levels in Layer 128 when generating edge levels.
Select Section › Interpolate from the ROADS menu.
Enter the Offset from centerline to interpolate as 0.000 and press ADD. Press OK to continue.
A point on the centerline of the road, at the ground level will be transferred to Layer 128. This level can now be raised or lowered, as needed using the Section › Absolute Change function.
You can generate edge levels using one of two possible methods.
Use this method if you want to re-design the existing super elevation of the road.
Use the Alignment › Edge Levels › Edit Super / Slave Super function to specify the edge levels. Run Alignment › Edge Levels › Generate Levels to calculate the edge levels using the vertical alignment points stored in Layer 128.
Remember to change the Layer for edge levels option to your Design Surface and not Layer 128.
Use this method if you would like to work with the existing super elevation of the road. The basic idea here is to generate edge levels manually by picking them up from the original ground cross-sections.
Select Section › Interpolate from the ROADS menu.
Press OK and add the following offsets to the list:
The reason why we use offsets of 0.5 and –0.5 instead of 0.0 is because the surveyed centerline may not exactly follow the specified horizontal alignment. The actual centerline may therefore be a little to the left, or a little to the right of the surveyed centerline.
The offsets 3.1 and –3.1 represent a point on the existing carriageway, close to the road edges. Extending a line from offset 0.5 to offset 3.1 should result in an accurate crossfall for each cross section. Press OK.
The cross section points on your design layer currently at offset 3.1 and –3.1 can now be extended at the current crossfall to the desired road widths.
Use the Section › Expand Shrink function to do this.
Press OK to move the point currently at offset –3.1, 5.5 meter to the left at the current crossfall. The point will then be at offset -8.6. Do the same for the right hand side.
If you used Method 1 to generate edge levels, or your design layer has only 3 points per cross section, you can use the Apply Template function.
If you used Method 2 to generate edge levels and you have more than 3 points per cross section on your design layer you must use the Add Template function instead of Apply Template. Add template simply adds compulsory and Cut/Fill details, as specified in the template, to the edges of the specified layer.
Select the Tools › Template Paths option and specify and number the templates to be used in the design. Select the Area/Volume › Add Template option.
Specify the template number to be used. Press OK
Define the Start chainage and Stop chainage as well as the Base layer and Batter layer as shown. Press OK to add the template.
If you used Add Template and you need to re-apply the template. You cannot simply run Add template again, because the cut and fill details will be added to the edges of whatever is currently in your design layer. You therefore need to remove the batter points before adding the template again.
To do this, select Section › Remove Points.
Press OK to remove the left hand side cross section points from PLC –3 to –99. Similarly you can remove the right hand side points by specifying:
Now you can re-add the template.
print friendly version