The Civil 3D Grading Optimization Extension: A Case Study
The Grading Optimization (GO) extension in Civil 3D is a relatively new feature in Civil 3D that has the capability to greatly reduce the time civil designers spend with grading tasks. The extension uses algorithms to iterate through TIN surface triangulation based on your own project specific design criteria. Two examples of grading criteria would be minimum/maximum slopes in an area and a building floor elevation. The GO works with simple polylines from your dwg file to derive a grading solution fast. It can also automatically transfer or update the results right back to Civil 3D. And it can return results with balanced earthwork much faster than I ever have produced.
I find the GO workflow to be fast and simple because it does not require specific elevation input for every object being constructed as you would need in a corridor or feature line grading model. The GO works primarily with simple 2D polylines at elevation 0.
As mentioned above, the Grading Optimizer works by manipulating surface triangles based on simple 2d polylines. It does not work with or recognize vertical curves used in profile designs. It will not compute cross slopes perpendicular from a centerline.
Due to the way the Grading Optimization Extension works I do not use it to produce a construction quality grading model. It can be used for very simple grading designs, but it is best used in my opinion, to provide a good rough surface that is already earthwork balanced. This optimized surface can be used to create a final grading model. This is done by either tracing layout profiles over the GO surface or superimposing elevations to feature lines from the GO surface for a final design and greatly reducing iterations with conventional grading techniques to balance earthwork.
I recently worked with a coworker to compare a project’s proposed grading model that was created using a combination of a corridor, gradings and feature lines to create a proposed stepped landscape energy storage site. The site grading consisted of using 6 retaining walls to create 7 low sloped equipment areas with vehicle access and two ponds. The grading task took some time. A couple of days of labor were spent designing and trying to balance the earthwork. The engineer did a great job getting the site to about 1200 CY of fill required.
The original grading model
After examining the proposed model I started a new dwg file, created a Datashortcut Reference to the existing ground surface and XRef’ed in the linework for the proposed conditions. I spent about 30 mins copying or creating polylines for different grading areas and objects (access aisles, walls, ponds) and ran the grading optimization tool. The result took our civil engineering team by surprise as the Grading Optimization tool reduced the earthwork to 4 CY of fill without running it to completion. It also significantly reduced the face area of the retaining walls and reduced the total area of cut/fill depths in excess of 5’.
Even as a new user, the Grading Optimization process only took about an hour and a half to this solution and the results were great. The resulting model still needed revisions for vehicle access vertical design and minimizing retaining walls, but it saved a lot of construction costs and design iterations to balance the earthwork.
Summary of Results
1. Earthwork
Original Grading: 1217 CY Fill
GO Grading: 4.5 CY Fill
2. Cut/Fill Depths
Original Grading: -12.8’ cut and 11.7’ fill
GO Grading: -9.5’ cut and 11.5’ fill
3. Retaining Walls
Original Grading: 3923 SF of face area
GO Grading: 2190 SF of wall face area (a 44% reduction)
4. Time Investment
Original Grading: 8 hrs.
GO Grading: 4 hrs.
Personally, I am sold on this relatively new feature and strongly recommend finding ways to make this part of your grading workflows. The GO is simple, easy to learn and has the capability to significantly reduce the time invested in grading tasks. If you are interested in learning how to use this great new Civil 3D feature follow the links below to a great web series by Autodesk employees, John Sayre, Charlie Ogden, and Valentin Koch.
Grading Optimization LIVE Part 1: The Grading Optimization Workflow -- https://www.youtube.com/watch?v=s1UCNW38qPI
Grading Optimization LIVE Part 2: Site Grading -- https://www.youtube.com/watch?v=pa4au__GuMY
Grading Optimization LIVE Part 3: Pond Design -- https://www.youtube.com/watch?v=3Xusn9-zW4c
Grading Optimization LIVE Part 4: Mass Grading -- https://www.youtube.com/watch?v=fDmZNOM9KXs
Grading Optimization LIVE Part 5 Subdivision Grading -- https://www.youtube.com/watch?v=S-VM3jaehgA
Grading Optimization LIVE Part 6 Retaining Walls -- https://www.youtube.com/watch?v=5RRHQS3mYpk
Author Bio: John Mayo, PE, CFM, CME, has worked as an engineer for private developers, municipalities, highway authorities (as a consultant) and utility companies (as a consultant). His projects have ranged from residential, commercial, retail and industrial sites, stormwater design (private site and municipal systems), flood analysis and culvert design, utility design and multi-county mapping, survey mapping (F2F and point cloud data extraction). John's CAD skills began with AutoCAD Release 9 and then with Softdesk 7 for civil engineering design. He is proficient with AutoCAD, Civil 3D, Map 3D, Infraworks, HydroCAD, Hec Ras, Revit, ArcGIS and other engineering and surveying applications.
Engineering Technology Manager – New Leaf Energy
Adjunct Professor – New Jersey Institute of Technology
Autodesk Expert Elite - Charter Member
