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Cut and Fill Quantity Calculation: How Can We Create Platforms and Slopes with Drops in Civil 3D?

The illustration above showcases earthwork designs incorporating slopes and vertical drops between platforms of varying heights.

Slopes and berms in MiTS #

In MiTS, generating such designs is straightforward, as the process is automated for users. Following the setup of platforms and slope parameters – such as platform height, slope direction, slope ratio, slope maximum height, and berm width – users only need to click the ‘Generate Slope’ button within the Earthwork Module.

Based on the disparity between the existing ground and platform height, MiTS initiates slope generation from the platform edges, and autonomously determines the number of tiers required and when to cease the slope.

Civil 3D Requires Feature Lines #

In Civil 3D, users need to use Feature Lines to design platforms incorporating slopes and berms.

Feature lines are lines with defined elevation points set by users; It can be an absolute elevation or elevation relative to the associated surface.

While this feature can indeed be utilized to depict the slopes and berms, it demands meticulous guidance from users, beginning with outlines representing the contours of the slopes and berms. Subsequently, users must manually calculate the height of the slope and determine the number of tiers required.

So, How Can Feature Lines Be Applied in Our Design? #

Drawing only with platforms line here.

Drawing sample with slopes and berms here.

Listed below are the steps involved in creating platforms with slopes and berms in Civil 3D.

Outlining Platforms and Slopes using Polyline #

Platforms #

  1. Create the outline following the shape of the platforms designed using ‘Polylines’.

  1. For side-by-side platforms that have a vertical drop (Retaining Wall) in between, users need to create a small gap in between the polylines established.

Slopes and Berms #

  1. With a known height and ratio of the slope, calculate the width of the slope.
  • Height of 4.57m and a ratio of 1.5, the width will be 6.75m
  • Height of 4.57m and a ratio of 2.0, the width will be 9.14m
  • The berm width will be 1.5m

  1. Offset the platform lines according to the width calculated.

To offset, simply select the line > Type in command Offset > Specify the offset distance, opt for Through > Input the distance > Press Enter

  1. Offsetting the lines for conjoined platforms will require users to trim the unnecessary edges as below.
  1. Also for the slope and berms part that have a vertical drop, a gap will be required as per the steps in ‘Outlining Platforms and Slopes Using Polyline – refer to Platforms section‘.

All platforms with slopes and berms have been outlined using polylines

Converting Polylines to Feature Lines #

  1. Covert the Polylines to Feature Lines and input the elevation for each corner. For assigning elevations, users can opt for

  • Elevation – The elevation input will be applied to all the corners
  • From gradings – The elevation of the corner will follow the elevation of the overlapping neighboring corner
  • From surface – The input elevation will be an offset value from the surface level

  1. Go to the Create Design section, click Feature Line > From the dropdown, click on ‘Create Feature Lines from Objects’ > Select the polylines > Press Spacebar 
  1. User will need to configure the Site, Style, Layer, and Conversion options > Click OK > Assign the elevations by selecting between the options available > Input the elevation value > Click OK

  1. If the feature line requires more points, user can insert elevation points as in the step below.

Select Feature Line > Under Edit Elevations, click ‘Insert Elevation Point’ > Specify distance for the point or user can also click directly on the feature line to place the point > The elevation will be detected by the program, simply press Enter

  1. For feature lines that have different elevations between the two ends, user can reinput the elevation under the Elevation Editor

Click on the feature line created > Click Elevation Editor > Double Click on the row to identify the corner (The corner will be highlighted in a green triangle) > Change the value under the Elevation column

Creating vertical drop between two platforms #

To create a vertical drop as in the image above, feature lines will be created connecting the opposite neighboring corners. The elevation of the feature lines should be defined following the value of the corners.

  1. Under Create Design, click on Feature Line > Opt for ‘Create Feature Line’ > Define the parameters (Site, Name, Style, and Layer) > Click OK
  1. Click on the first point of the feature line (Any corner will do) > Spacebar > Ensure the elevation shown is the correct value; If not, change the value accordingly > Spacebar
  1. Specify the endpoint > Ensure the elevation shown is the correct value; If not, change the value accordingly > Enter
  1. If user is unsure of the exact elevation, do note that the elevation value can be configured under the Elevation Editor as in the step here.

Creating Surface from Feature Lines #

  1. Select all the feature lines one by one > Go to Modify section > Click ‘Add to Surface as Breakline’.
  1. Create Surface dialog will appear, user can opt to follow the Name given or Change the surface name accordingly > Click OK.
  1. Add Breaklines dialog will appear > User may write in the Description or leave it blank > Type is set to Standard > Click OK.
  1. The surface will be created automatically by the program. User can change the Surface Style to suit their preferences.
  1. Select the surface created > Go to the General Tools section, and click on the ‘Object Viewer’ to view the object from various angles.

Trimming Unwanted Surfaces #

Civil 3D heavily relies on TIN Surfaces to depict the topographical features of Earthworks. The program will connect all the 3D points scattered across the area through a series of edges, forming a network of triangles known as triangulations.

While triangulations are effective for representing terrain with numerous scattered points, they are less suitable for cases like platform representation, where there are limited 3D points defined by the feature lines. This leads to the creation of excess triangles for the surface, affecting appearance and the Cut/Fill volume.

As a solution, users can choose to trim the triangles by removing unwanted lines from the triangulations as demonstrated below.

Select the Surface > Go to Modify section > Click ‘Edit Surface’ > Select ‘Delete Line’ > Select the unwanted lines that need to be removed

Conclusion #

The steps described above show how the platforms with slopes, berms, and drops can be made in Civil 3D.

However, it’s important to understand that when working on real projects with lots of platforms, slopes, berms, and various terrain elevations, the process becomes more demanding. As the project complexity rises, so does the amount of work needed to accurately model and represent the terrain features.

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