Grading and earthworks volumes
Site grading shapes the ground for buildings, car parks and drainage. Learn to model graded surfaces with feature lines and calculate cut and fill.
In this lesson you will
- Model pads and slopes with feature lines
- Create grading objects to target surfaces
- Calculate cut and fill with volume surfaces
- Balance earthworks
Feature lines
Feature lines are 3D lines with elevations at each vertex — the edges of pads, kerbs, swales. Create them from polylines or directly, then set elevations and grades with the Elevation Editor or Set Grade/Slope Between Points. They can be added to surfaces as breaklines.
Grading objects
- 1Create a feature line for a building pad at the finished level.
- 2Home › Grading › Grading Creation Tools; choose a grading group and criteria (e.g. Grade to surface at 1:3).
- 3Pick the feature line and the side; the grading daylights to EG.
- 4Add an infill grading for the flat pad.
- 5Create a surface from the grading group.
Volumes
The Volumes Dashboard (Analyze tab) compares two surfaces — existing and proposed — to give cut, fill and net volumes, with factors for bulking and compaction. A TIN volume surface can also be shaded and labelled with cut/fill depths to show where earth moves.
Balancing
Importing or exporting soil is expensive. Raise or lower the pad and grades to bring cut and fill closer to balance, remembering that site-won material may need treatment and that topsoil is stripped and reused separately. Report volumes with the assumptions you used.
Quick reference
| Command / tool | How to start it | What it does |
|---|---|---|
| Feature Line | Home › Feature Line | 3D grading lines |
| Grading Creation Tools | Home › Grading | Slopes to surfaces |
| Volumes Dashboard | Analyze tab | Cut/fill between surfaces |
| Elevation Editor | Feature line tools | Sets vertex elevations |
Common mistakes
Volumes look far too large.
Check the surfaces overlap only where intended and units are metres.
Grading fails to daylight.
The target surface doesn't extend far enough or the slope never reaches it.
Exercise
Building pad earthworks
- Create a 30 × 20 m pad feature line at a level near the middle of your site's range.
- Grade it to EG at 1:3 with an infill.
- Build a proposed surface and compare it with EG in the Volumes Dashboard.
- Adjust the pad level to approach a cut/fill balance and record the result.
You should end up with: A graded pad with balanced earthworks and reported volumes.
Checklist
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Lesson quiz
Feature lines have elevations at their vertices.
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