Earthwork is the first number an estimator asks for, and the one that moves most each time the profile changes. Doing it by hand on cross sections takes a day. In Civil 3D, once the corridor and sample lines exist, it takes a few dialogs, and the report updates when the design changes.
This article computes Civil 3D earthwork volumes by the average end area method in four illustrated steps. The data is the 461 m route of this series, with the corridor from Civil 3D corridor and sample lines from Civil 3D cross sections. The result is the route's real cut and fill table: about 4,770 m³ of cut and 2,460 m³ of fill.
How Civil 3D computes earthwork
Civil 3D compares two surfaces on each cross section:
- EG (Existing Ground): the natural ground.
- DATUM: the underside of the road structure, a surface built from the corridor.
Ground above the datum is cut, below it is fill. Cut and fill areas are measured on each section. The volume between two neighbouring stations is the average of the two areas times the distance between them. That is the average end area method, the usual approach for road packages.
So three things must exist first: the existing surface, a corridor surface, and a sample line group that samples both. This chain is taught end to end in the Institute's online Civil 3D course.
This differs from comparing two surfaces directly. A direct comparison gives one total for the route. Section-based volumes give a figure per station, which design and measurement packages need, because each stretch is built and paid by station.
Step 1: Create the corridor surface (DATUM)
Select the corridor and click Corridor Surfaces on its contextual tab. Click the button that creates a new surface, then choose the link code that forms it.
| No. | Item | Meaning |
|---|---|---|
| 1 | Create surface button | Adds a corridor surface to the list |
| 2 | Specify code: Datum | The underside of the structure. Top is the finished top, used for display, not for earthwork |
| 3 | Plus button | Adds the chosen code to the surface |
A corridor surface needs a boundary or it will triangulate outside the road. On the Boundaries tab, right-click the surface name.
| No. | Item | Meaning |
|---|---|---|
| 1 | Boundaries tab | The corridor surface boundary |
| 2 | Corridor extents as outer boundary | Uses the outer edge of the corridor, the toe of slopes, as the boundary |
Click OK and choose Rebuild the corridor. Prospector now shows a new surface, CORRIDOR TUYEN CHINH - (1).
Step 2: Sample the corridor surface
A sample line group created before the corridor surface does not know about it. Select a sample line and click Sample More Sources.
| No. | Item | Meaning |
|---|---|---|
| 1 | Sampled sources | Three sources: existing ground, the corridor, and the new corridor surface |
| 2 | Add >> | Moves a source from Available to Sampled |
Skip this and in the next step the DATUM cell offers only the existing ground, so volumes cannot be computed.
Step 3: Run Compute Materials
Select a sample line. The contextual tab has two commands in its Launch Pad panel.
| No. | Item | Meaning |
|---|---|---|
| 1 | Compute Materials | Computes material areas and volumes at every station |
| 2 | Generate Volume Report | Produces the volume table |
Click Compute Materials, pick the alignment and sample line group, click OK.
| No. | Item | Meaning |
|---|---|---|
| 1 | Quantity takeoff criteria | Cut and Fill, the stock earthwork criteria |
| 2 | Volume calculation method | Average End Area |
| 3 | EG | DIA HINH TU NHIEN on both rows |
| 4 | DATUM | The CORRIDOR TUYEN CHINH surface on both rows |
| 5 | OK | Compute |
Take care with "Click here to set all": the list holds two surfaces and their order can change after adding a source. Read the Object Name column after choosing. EG must be the existing ground, DATUM the corridor surface. Swapped, cut and fill swap too.
Step 4: Export the volume report
Click Generate Volume Report.
| No. | Item | Meaning |
|---|---|---|
| 1 | Select material list | The list from step 3, Material List - (1) |
| 2 | OK | Opens the report in a web browser |
The report opens as an HTML page that can be printed or copied into a spreadsheet. Keep the drawing and the report together: the report is a snapshot, while the material list in the drawing stays live and recomputes whenever the corridor or the sample lines change.
| No. | Column group | Meaning |
|---|---|---|
| 1 | Cut Area, Cut Volume | Cut area at the station (m²) and cut volume since the previous station (m³) |
| 2 | Fill Area, Fill Volume | Fill area and volume |
| 3 | Cum. Cut, Cum. Fill, Cum. Net | Running totals of cut and fill from the start, and cut minus fill |
The table matches the profile. From 0+000 to 0+200 the design is above ground, so there is only fill; the largest fill area is 17.77 m² at 0+165. From 0+220 the road cuts into the hillside and cut grows; the largest cut area is 57.71 m² at 0+360.
| No. | Row | What it shows |
|---|---|---|
| 1 | Station 0+340 | Cumulative net volume turns from negative to positive: by here cut exceeds fill |
| 2 | End station 0+461.01 | Route totals: cut 4,767.49 m³, fill 2,458.09 m³, surplus cut 2,309.40 m³ |
A surplus of more than 2,300 m³ means the cut can fill the early stretch with material to spare. In practice not all cut is reusable: topsoil and weak soils are wasted, and fill needs a compaction factor. The Reusable Volume column is where reusable material shows up when the criteria include it. To balance better, lower the profile at the start or raise it over the hill, then rerun step 3. The report recomputes from the new corridor.
Common problems with Civil 3D earthwork volumes
Odd areas at stations near the survey edge. On the sample route the end station 0+461.01 shows a cut area of 405.76 m², seven times the largest real one. It sits at the edge of the survey, where the side slope found no ground (Civil 3D reported "No sideslope intersect found" when building the corridor). The last stretch's volume is inflated as a result. Scan the area columns for outliers, and drop stations outside the survey or extend the terrain data.
No corridor surface in the DATUM cell. The corridor surface was not sampled; see step 2.
Cut and fill reversed. EG and DATUM were swapped. Reopen Compute Materials and read the Object Name column.
Volumes unchanged after a design edit. The corridor was not rebuilt, or its surface is out of date. Rebuild the corridor and rerun Compute Materials.
Running totals differ from a hand sum. The first station's volume is always 0 because there is no previous station to average with. Summing the Cut Volume and Fill Volume columns gives the final totals; a mismatch usually means rows were lost when copying into a spreadsheet.
Volumes too low on curves. Sparse stations on curves distort the average end area. Add stations at curve start, end and middle when creating sample lines.
Frequently asked questions
Can the Civil 3D volumes go straight into an estimate?
They are the source figures. The estimator still checks outlier stations, removes pavement layers if the criteria count only earth, and applies factors as required.
How do I separate topsoil stripping?
Create a surface for the base of the topsoil and use criteria that include a stripping material. Each material becomes a column in the report.
Is there a quick total without cross sections?
Yes: compare the two surfaces directly with the Volumes Dashboard for an instant total. It does not give the per-station table road packages require.
Why does the report open in a browser?
The volume report is an XML file transformed by an XSL style sheet into an HTML page. The Select a style sheet box in Report Quantities picks the layout; other style sheets in the same folder give different column sets, and a company can edit one to match its own quantity table.
Can I put the table into the drawing?
Yes. Civil 3D can insert a total volume table into the drawing from the same material list, and section views can carry a volume table beside each section. Both update when the corridor is rebuilt, unlike a pasted spreadsheet.
What about pavement quantities?
Use criteria with structural materials (Corridor Shapes) and map the pavement layer shapes. Each layer's volume appears as its own column.
Related articles
Earthwork is the last link in the chain of contour lines, alignment design, profiles, corridor and cross sections in Civil 3D. What is Civil 3D explains why quantities follow the design. Autodesk's overview is in About Generating Material Lists for Sample Line Groups.
Earthwork, pavement and quantity tables for estimates are session 5 of the Institute's online Civil 3D course. Estimators can continue with the construction cost estimating course.