Occasionally, due to flat grades and twisting horizontal alignments, it's possible to accidentally create "water traps" in the ditch line. Geopak provides a very easy way to check for these and correct them.
The first step is to check that all the ditches flow. This is done by executing the Profile Grade application from the Cross Section Reports dialog, while in the cross section file. This application will search for the lowest elevation along the proposed finish grade element path on each side of centerline, and store a profile for each side.
Invoke the XS Report dialog by using the MicroStation pull downs:NOTE: A more detailed explanation of the Profile Grade report can be found by clicking here.
APPLICATIONS > GEOPAK ROAD > CROSS SECTIONS > REPORTS... or from the Road Tools icon as shown below:
The XS Report dialog will appear as shown below. Click User and fill out the Report Header Dialog box. This Report Header information can be saved by clicking on File and selecting the path and file name to be saved. When finished, press Profile Grade on the XS Report dialog.
This brings up the Profile Grade Report dialog as shown below:
Once again, for a more detailed explanation of the Profile Grade report and filling out the dialog box, please click here.
After filling out the Profile Grade Report, similar to the one above, click on Apply. The profiles LT_LOW and RT_LOW will be stored into the GPK file.
The text file, low_prof.pgr really isn't necessary, but provides a text file illustrating the stations and elevations of these "low points".
Open a 2D file and use the Design and Computation Manager to draw the stored profiles.
Use the 2 D&C Items (LT Low Profile and RT Low Profile), shown below for drawing these low point profiles:
The drawing below illustrates an apparent water trap at station 50+640.
This is because the lowest point along the left side of the proposed finish
grade elements at station 50+640 is higher than station 50+660.
If the road was to be constructed "as is" the first time it rained, a puddle
would form in the ditch and it would have to be re-graded to drain.
The designer would probably get a phone call from the Project Engineer complaining
about a "poor" design.
A "special ditch grade profile" should be included as part of the design to eliminate this, thus avoiding the phone call.
Simply review the left and right "low point profiles" drawn by D&C Manager and store a special ditch profile to correct the drainage problem:
Once the profile is stored, it must be entered into the proposed cross section "run" as shown below:
Multiple special ditch profiles can be entered concurrently on each side, by separating each profile with a comma.
When the proposed cross section run is processed, the ditch line (for each affected cross section) will automatically extend down to the elevation along the special ditch profile. The "Special Ditch Profile Elevation = X,XXX.XX" text will be automatically placed.
When all of the "water traps" have been isolated and corrected with the special ditch profiles, the Profile Grade Report can be reprocessed. New low point profiles can then be drawn with the D&C Manager to verify that all ditches will drain.
