In this topic you will learn how to design vertical alignment for a highway using ESurvey CADD Road Design module.
In the previous topic you have learnt how to import surface data, base map, and tangent and design horizontal alignment. Once the horizontal alignment is done, we can go ahead with Vertical Alignment design. In Road Design module all the functionalities related to Vertical Alignment are defined in Vertical Alignment Tab. You can design vertical alignment for all the alignments that you have created in the horizontal alignment tab weather it is parent alignment, offset for parent alignment or those which are imported as alignments from cad package. In vertical alignment tab, longitudinal section drawing gets created, which will automatically have bands related to horizontal alignment. We can also enable bands related to each vertical alignment, which gets created automatically. After we design the Vertical alignment derived Formation levels will further reflect in Cross Sections which you can be created in Cross Section Tab.
1. Existing Profile Button settings
You can design vertical alignment for all the alignments that you have created in the horizontal alignment tab. Normally vertical alignment is done either for Project center line or LME and RME in case of divided carriage way. Vertical design is also done for service road and drain center. All that can be achieved in Vertical design tab. Before we design vertical alignment you have to extract elevation for an existing alignment profile.
1. To extract elevation along an alignment ESurvey CADD allows various settings. Click on Existing Profile button to open Profile setting window.
2. Select all the alignment names for which vertical alignment design has to be created. We can define chainage interval for vertical alignment irrespective of what chainage interval we have defined in horizontal alignment. We can create elevations either at chainage points or at all the surface edges, that means ESurvey CADD will extract elevation from the TIN surface wherever alignment intersects with TIN. If you select “Add chainges at the change points” elevations for all the change points are also generated.
2. Importing the vertical alignment tangents
Export the Longitudinal section drawing to cad package, after extracting the elevations for alignments as explained in the previous step. Now draw the tangent lines for alignment. We can export the tangent line from CAD by selecting “Export LS data by selecting polyline(LSEXP)” menu under “Road Design” menu of “esurvey cad menu”. The program will ask you to provide input like drawing scale, datum etc., which can be provided by referring to Longitudinal Section drawing.
After exporting the tangent line from CAD, it can be imported to ESurvey CADD via Import button after selecting respective alignment from drop down. That means importing tangent in vertical alignment is similar to the way you import tangent lines in horizontal alignment. A similar procedure can be repeated for many alignments.
3. K Value Setting
Before we go ahead and design vertical profile, we have to define the minimum curve length. Click on K Value button to do the setting.
For achieving best results you can set K Value for sag and crest curve. By default 44 is K value for sag curve and 74 is the value of crest curve. You have the liberty of setting different values for all these parameters, depending on the values you set here, software will further design the vertical curve.
4. Designing the vertical profile.
Select the alignment for designing, all the PVI points of the selected alignment are listed, you may select all of them or by referring to gradient you can select only few PVI’s and then click on Design button.
Software will design vertical curves for all the PVI’s. You may repeat the same for different alignments. In order to see the vertical table showing the curve details you can click a button Vertical curve table and vertical curve table settings window will appear, where you can make necessary setting such as display, Line color, text color, Text height and table offset and close window and view the curve tables in the drawing.
There may be some VIP points which are not designed. The reasons could be that consecutive curves are overlapping or a curve could not be fitted as per K Value settings. In the next step you can change parameters of designed curves and you can also specify curve values for VIPs for which software has not fit a curve.
5. Editing the Vertical Profile
Select the alignment from the drop down for which you want to edit the vertical curves. Select the “curve details” sub tab. It may be noted that the curves which are not designed are highlighted in red color in the table. Select the curve, which you want to modify. Click on Edit curves button.
Change the curve length either directly changing it or by changing the k value and update. If you wish to refer IRC Values, i.e., abstract of IRC 73, then click on the Reference Table button.
You can generate many reports related to Alignment with details of each curve.