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OBRAS ONSITE · free site calculators · plant & earthworks

Plant & Earthworks

How many buckets, which machine, and what it really costs to hire. Typical GP-bucket capacities and burn rates - your machine's spec sheet and the geotech report win.

🚜 Machine bucket loads

Machine Loose volume to move (m³)
Typical GP bucket, 90% fill factor. Cycle times are steady-dig estimates - tight access and deep digs run slower. Get loose volume here →

🔧 Trench & backfill

Length (m) Width (mm) Depth (mm) Pipe dia (mm) Bedding (mm)
Backfill = dig − bedding − pipe displacement. Spoil bulks ~1.3× on the way out. Compact backfill in 150-300 mm lifts.

⚠ Batter & benching check

Excavation depth (m) Ground
WHS rule of thumb: excavation deeper than 1.5 m needs shoring, benching or battering - and a competent/engineered call on the method. These ratios are indicative only; the geotech report and your excavation permit govern. Never enter an unsupported deep trench.

⏱ Machine productivity

Machine Loose volume (m³)
Rate = bucket × 90% fill × cycles/hr × 75% job efficiency (trucks, spotting, services). Use it to compare machine sizes before you book the hire.

⛽ Fuel burn

Machine Hours Diesel $/L
Typical average burn under normal load. Dry hire? This is the bill on top of the rate - budget it before you sign.

🤝 Wet vs dry hire

Wet rate ($/hr, machine + operator) Dry rate ($/hr) Your operator ($/hr all-in) Fuel ($/hr)
Dry hire also means your VOC, your insurance exposure and your damage risk. True operator cost here → · VOC register →

🛣 Hardstand & road base

Area (m²) Compacted depth
Order loose ×1.25 for compaction; tonnage at ~2.24 t/m³ compacted DGB. Compact in max 150 mm lifts.
Plant packs, VOCs & excavation SWMS in the Obras Onsite catalogue · tag the fleet with Plant QR · All free tools →

This is a practical site-management tool. It is not legal, engineering or regulatory advice and does not guarantee compliance or a satisfactory inspection outcome. Requirements may vary by jurisdiction, project, contract and circumstances.

Want a person to look at it?

The tools above are free and yours to use. When you need the paperwork behind them reviewed by someone who has run sites, Obras HSE Services is a live consulting business in south-east Queensland.