SPECIAL DITCH GRADES

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 palette, while in the cross section file. This application will search for the lowest elevation on each side of centerline, along the proposed finish grade elements, and store a profile for each side.

To invoke this application:

APPLICATIONS > GEOPAK ROAD > CROSS SECTIONS > CROSS SECTION REPORTS Then........click on Profile Grade.

After filling out the Profile Grade Report palette, similar to as shown above, click on Apply.

Open a 2D file and use the Design and Computation Manager to draw the stored profiles. It will be helpful to draw these at different colors for easier viewing.

Until the Metric.ddb and English.ddb files are modified to draw these at different colors, just draw the first profile, toggle "graphic group lock" ON, change color, and then draw the second one using the default color.

The drawing above illustrates an apparent water trap at station 12+080. This is because the lowest point along the left side of the proposed finish grade elements at station 12+100 is higher than station 12+080. 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" 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:

The special ditch profiles can be stored two different ways:

Storing a Special Ditch Profile through COGO:

Storing a Special Ditch Profile using Layout Vertical Alignment:

The above method is easily done using the Dynamic button and snapping to the graphic. Then save it:

Once the profile is stored, it must be entered into the proposed cross section input file as shown below:

/* special ditch profiles */

define "LT PROF" L12_080

define "RT PROF" dummy

NOTE: The "special ditch profile" execution is performed within the criteria file FH_SS3.X08.

Multiple special ditch profiles can be entered concurrently on each side, by separating each profile with a comma.

When the proposed cross section input file 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 = XXXX.XX" text will be automatically placed.

BEFORE....

AFTER....

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.

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