Grade a site using grading objects

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Grading objects in Civil 3D can be used for a variety of terrain modification and land development tasks

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that require exact control over slopes and elevations.

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Common applications include creating level building pads,

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designing detention or retention ponds that manage stormwater runoff effectively,

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and shaping landscapes, roadway embankments, and more

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to ensure proper drainage and sustainability.

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To demonstrate the use of grading objects,

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a previously created drawing is already open in Civil 3D.

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An added feature line already has elevations assigned

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and will be used as the base of the design.

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On the Home tab, Create Design panel, expand Grading Object

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and select Grading Creation Tools.

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This displays the Grading Creation Tools toolbar,

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where you can set up your grading object by working from left to right across the toolbar.

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First, click Set the Grading Group.

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In this example, there are no current grading groups,

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so a new one needs to be created.

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Enter a Name, such as “Pond”, enable Automatic surface creation,

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and leave the Surface style setting as is.

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If you want to check the volume,

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enable Volume base surface,

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and then set the Base surface—here, existing ground, or EG, is selected.

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Click OK.

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In the Create Surface dialog, leave the default name,

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which is the same as the grading group name, and then click OK to create the surface.

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In the Grading Creation Tools toolbar, notice that the Group is now set to Pond

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and the volume Surface is set to existing ground.

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The surface is already set, so you do not need to set the target surface.

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Grading layers are also not required due to the styles that are set.

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Click Select a Criteria Set, and since the Basic Set has everything required here, simply click OK.

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Then, expand the Criteria drop-down and select a criteria.

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In this case, select Grade to Distance to create a semi-flat surface on top of the pond.

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Next, expand the Grading Creation Tools drop-down and select Create Grading.

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When prompted, select the feature line, then click inside to grade that area first.

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Click Yes to apply the grading to the entire length.

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To specify a distance, you can either select a point in the drawing or type an exact distance.

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Here, type 3, and then press Enter.

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Finally, set the Format.

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For this example, since you want the grading to have a -2% slope to the inside of the pond, select Grade,

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and then enter -2.

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The surface is generated.

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Press ESC to complete the command.

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To review the grading object in 3D, right-click the surface and select Object Viewer.

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In the Object Viewer, pan and orbit the drawing to see that the grading is sloping into the inside of the pond.

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Next, apply a grade to the outside of the pond.

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From the Grading Creation Tools, expand the Criteria drop-down,

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and this time, select Grade to Surface.

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Click Create Grading.

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Select the feature line, pick a point to grade the area outside of the pond,

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and apply the grade to the entire length.

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Set the Cut Format to Slope, and press ENTER to accept a 2.00 : 1 slope.

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Then, set the Fill Format Slope to 3.00 : 1.

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The surface is created.

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Open the Object Viewer again to see the grading outside of the pond,

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with a slight rim at the top,

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but with no triangles or contours in the center.

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This is because an infill needs to be added.

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First, however, you need to set the depth of the pond.

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Back in the toolbar, set the Criteria to Grade to Relative Elevation,

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and then click Create Grading.

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Select the inside line of the grading object as the feature line and apply the grading to the entire length.

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Specify a Relative Elevation of -3 for a pond depth of 3 feet,

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and then set the Format to a Slope of 2.00 : 1,

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making it the same on both sides.

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Press ENTER to finish the command.

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Reviewing the surface in the Object Viewer, it now looks like a pond,

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but you still need to add an infill.

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From the toolbar, expand the Create Grading drop-down and select Create Infill.

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In the drawing, pick a point on the inside, then press ENTER.

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Now, in the Object Viewer, you see that it has the triangles to the inside.

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With the surface completely infilled, you can optimize the grading.

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From the toolbar, expand the Grading Utilities drop-down and select Grading Volume Tools.

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The Grading Volume Tools open and display the Cut, Fill, and Net Volumes.

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Here, you can click Lower the Grading Group to slowly reduce the amount of fill.

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Even better, to balance the Cut and Fill towards a target net volume,

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click Automatically Raise/lower to Balance Volumes.

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The Auto-Balance Volumes dialog opens.

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In this case, leave the Required volume set to 0 cubic yards and click OK.

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After a moment, the grading object changes.

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Select the object, then open the Object Viewer.

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There is now both cut and fill going around the outside of the pond,

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and the inside has an even, 3-foot depth.

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Now you can use the Grading Creation Tools to create and modify grading objects in Civil 3D.