Civil 3D cross sections: from sample lines to sheets and earthwork volumes, without redoing them on every change

Sample lines are created on the alignment and stored in a sample line group. The most common ways to create them:

• By range of stations: every 50 ft on tangents and every 25 ft on curves, for example, from a start station to an end station.
• At corridor stations: one line at every point where the corridor computes its section.
• At a specific station: for culverts, section changes or control points.

The swath width on each side must cover the full corridor including daylight. If it falls short, the section is clipped and the volume is incomplete.

Sources are chosen in the group: existing ground, the corridor and its surfaces, such as the subgrade. Anything not in the sources won't show in the section.

With the group ready, create the section views, usually many at once (Create Multiple Section Views). The key decision is placement:

What controls the result:

• The group plot style: how views are arranged, in rows or columns, and their spacing.
• The section view style: the grid, horizontal and vertical scales, and titles.
• Bands: the data rows under each view, such as offsets and elevations.
• Labels: grade elevations, edges, slopes and areas.

Getting these styles right once, in your firm's template, is what lets the next road come out the same with no extra work.

If the views were created with the production option, Civil 3D can build the sheets automatically with Create Section Sheets, on the Output tab: pick the alignment, the sample line group and the section view group, and it creates one layout per sheet.

What's usually missing to make the sheet submittal-ready is what's specific to each firm or agency: a title block showing the stations on each sheet, numbering, file naming and the format of the earthwork table. That's where the hours go.

Volumes are computed by comparing surfaces at each section:

1. Quantity takeoff criteria: define what gets compared, for example existing ground against the corridor subgrade to get cut and fill.
2. Compute Materials: applies those criteria to the sample line group.
3. Volume tables: the total volume table gives cut, fill and cumulative volumes by station. Civil 3D also builds the mass haul diagram.

By default, Civil 3D uses the average end area method, the one most plan sets use. The result depends on the interval: with sections every 50 ft, an abrupt terrain change between two sections isn't captured.

• The corridor or existing ground doesn't show in the section. It's missing as a source in the sample line group.
• Sections don't change after editing. The corridor is out of date: rebuild it. Other corridor errors, such as slopes that don't daylight or holes in the surface, are covered in the Civil 3D corridor tutorial.
• The section is clipped. The sample line swath is narrower than the corridor with its daylight.
• Views overlap or don't fit the sheet. The sheet template or the group plot style doesn't match the chosen scale.
• Volumes don't match the manual calculation. The criteria compare the wrong surfaces, or the section interval differs from the one used by hand.
• Editing a section. The corridor section editor lets you modify the section at a specific station; the change is applied to the corridor.

Civil 3D's native workflow updates the geometry. What it doesn't do on its own is whatever depends on your rules, and that's what repeats the most:

• Sample lines at the stations in the plans, read from a table.
• Labels in your firm's format: elevations, widths, slopes and areas.
• The earthwork table in the agency's format, generated from the model's volumes.
• Complete sheets: title block with stations, numbering and file naming, regenerated after each change.

With a plugin, all of that is regenerated in minutes after every review comment. We explain it in automated plan production.