📖 Construction Field Guide · Earthworks

Earthworks, explained for the field.

Granular A and B, tonnes vs cubic metres, swell and shrink, compaction lifts, trenches and pipe bedding — in plain language, with the tools to go with them.

Granular & aggregates Volumes & conversions Compaction Excavation & trenches Field tips

1Granular & aggregates

The two granulars you'll order most are A and B — and they're not the same thing.

  • Granular A — a well-graded, fully crushed granular (typically up to about 25 mm). It compacts into a firm, drainable layer and is the standard base directly under asphalt or concrete.
  • Granular B — a coarser granular (up to about 150 mm for Type II). It's the deeper sub-base and bulk fill — the "bulk" of the road structure.

Think of it as a stack: Granular B does the heavy lifting down deep, Granular A provides the smooth, dense platform the pavement sits on. On asphalt work you'll see this exact stack under the lifts — see the asphalt field guide for the full cross-section.

CalculateGravel / granular calculatorArea, depth and density → tonnes of granular for the base. ConvertAggregate conversion calculatorSwitch between tonnes, cubic metres and yards.

2Volumes & conversions

The same material has three different volumes depending on where it is.

Same material, three volumes BANK in the ground (1.0 m³) LOOSE excavated / in the truck swells ~20–30% COMPACTED back in the fill shrinks ~10–15% order by loose volume in the truck — it comes out bigger than the hole you dug
Bank → loose → compacted: excavated material swells in the truck and shrinks again when compacted.

Digging loosens material and it takes up more space in the truck (swell); compacting it back squeezes it into less space than the original hole (shrink). Swell and shrink vary by material — rock swells more than clay, and some materials barely shrink at all. Use the project's assumed factors when you can; otherwise treat 20–30% swell and 10–15% shrink as starting points, not guarantees.

Tonnes = Volume (m³) × Density (t/m³)

A common working density for granular base is around 2.0–2.2 t/m³ compacted (lighter loose). Check the material's actual density — it changes the truck count.

BalanceCut & fill calculatorBalance excavation volumes across a site. ConvertCubic yard / metre calculatorQuick volume conversions for materials. Run the jobEarthwork workflowVolume, swell, haul planning and production. ConvertUnit converterLength, area, volume, mass — metric and imperial.

3Compaction

Fill is placed in thin lifts and compacted to a spec'd percentage — never dumped deep and rolled.

Compaction % is field density ÷ maximum (Proctor) density × 100. Fill is placed in lifts (commonly 150–300 mm loose per lift, depending on the material and equipment) and each lift is compacted before the next goes on. The spec sets the required % (95–98% is typical for structural fill) and the test method.

Fill is placed in thin lifts LIFT 4 LIFT 3 LIFT 2 LIFT 1 SUBGRADE each lift compacted before the next goes on typical loose lift: 150–300 mm — deeper only if the spec and equipment allow
Thin lifts, each compacted before the next — that's how deep fill gets dense.
Field tipCompaction tests are taken at the surface of a finished lift. If the material isn't at the right moisture, more rolling won't fix it — dry or wet fill won't reach density no matter how many passes you make.
CalculateCompaction / distribution reportTurn density readings into a distribution summary. RecordField QCLog compaction results by station and keep the report.

4Excavation & trenches

A trench isn't just a hole — it's bedding, pipe zone, backfill and cover.

Trench cross-section PIPE BACKFILL — compacted lifts PIPE ZONE / BEDDING BEDDING UNDER PIPE cover width
Bedding under the pipe, granular around it, then backfill in compacted lifts.

The bedding under the pipe is shaped and compacted so the pipe sits evenly (never on hard spots). The pipe zone around the pipe is usually granular or sand, placed carefully so the pipe isn't damaged. Above that, backfill goes in compacted lifts. Excavation also needs to be sloped or benched (or shored) to keep it safe — never work in an unsupported trench.

Field tipCompact the pipe zone by hand or with light equipment, not the big roller — you'll crush or shift the pipe, and nobody finds out until the test fails.
CalculatePipe volume calculatorFlow and volume for pipes and culverts. EstimateCut & fill calculatorWork out the excavation quantity before the machines start.

5Field tips

The stuff you learn watching the dozers.

Field tip — orderingOrder granular by tonnes but plan in cubic metres — and account for swell if you're hauling it off site. The truck count changes with both.
Field tip — moistureGranular compacts best near its optimum moisture. Too dry, add water and mix; too wet, spread and let it dry. Rolling wet material just makes soup.
Field tip — recordsMark the top of each lift and where compaction tests were taken. If a test fails later, the record tells you exactly which lift to fix.

Put this guide to work.

Calculate the volumes, plan the haul, and carry it all into the earthwork workflow and daily report.

Open the Earthwork Workflow →