Example data table
Use these sample values to test the calculator quickly.
| Zone | Length | Width | Existing depth | Target depth | Overdepth | Slope (H:V) | Irregularity |
|---|---|---|---|---|---|---|---|
| Approach Channel | 300 | 80 | 12 | 15 | 0.30 | 3 | 1.05 |
| Turning Basin | 250 | 250 | 13 | 16 | 0.30 | 4 | 1.07 |
Formula used
- Plan area: A = L × W
- Average cut depth: d = max(0, Target − Existing) (+ Overdepth if enabled)
- Prismatic volume (in-situ): V = A × d
- Side slope adjustment (optional): Vwedge ≈ Perimeter × (Slope × d) × (d / 2)
- Irregularity: V = (V + Vwedge) × Irregularity
- Loss allowance: V = V × (1 + Loss)
- Loose volume: Vloose = V × Bulking
- Mass estimate: M (t) = V × Density (t/m³)
How to use this calculator
- Select your input units and dredging work type.
- Set bulking, losses, density, and optional logistics capacities.
- Add zones for each footprint: channel, basin, berth pocket, or turning circle.
- Enter existing and target depths; enable overdepth if required.
- Enable side slope adjustment if the cut includes sloped sides.
- Click Calculate to view totals and the zone breakdown above the form.
- Use the download buttons to export the same results to CSV or PDF.
Seaport dredging volume planning guide
1) Why volume accuracy drives cost
Dredging contracts are commonly priced per cubic meter, so a small percentage error becomes a large budget swing. A 5% variance on 250,000 m³ equals 12,500 m³ of unplanned work. Early estimates should therefore include realistic allowances for survey uncertainty, shoaling pockets, and production losses.
2) Zoning your footprint for better control
Breaking the project into approach channels, turning basins, berth pockets, and flare transitions improves traceability. For each zone, the calculator uses plan area and average cut depth to compute prismatic in-situ volume. Multi-zone modeling also supports phased dredging and separate pay items. Model transitions separately to avoid overestimating wide areas at deep cuts often.
3) Typical bulking, losses, and logistics
In-situ sediment expands when excavated. Bulking (swell) factors of 1.10–1.40 are frequently used depending on material and water content. A loss allowance of 2–5% is often applied for spillage, turbidity, rehandling, and trimming. The calculator converts adjusted in-situ volume to loose volume for truck trips or hopper loads.
4) Side slopes and overdepth allowances
Channels and basins rarely cut as perfect vertical prisms. Where side slopes are dredged, extra wedge volume occurs around the perimeter. Overdepth (for example 0.20–0.50 m) may be specified to account for allowable tolerance and rapid re-siltation. Enable these options to align the estimate with spec requirements.
5) Using results for schedules and disposal
Once volume is known, planners can compare plant productivity. If a dredge produces 3,000 m³/day (loose), a 120,000 m³ task is roughly 40 working days before weather and downtime. Mass estimates (tonnes) support barge stability checks and disposal cell capacity planning. Exported CSV/PDF outputs help document assumptions for tenders and approvals.
FAQs
1) What is the difference between in-situ and loose volume?
In-situ is the volume in the ground. Loose volume is excavated, expanded material. The calculator applies a bulking factor so you can estimate transport needs and hopper or truck capacities.
2) Which bulking factor should I use?
Start with 1.20–1.30 for mixed sands and silts. Use higher values for very soft, wet sediments. Confirm with local geotechnical data, past dredging records, or production measurements.
3) Why add a loss allowance?
Losses cover spillage, overflow, trimming, and rehandling. A 2–5% allowance is common for planning. Use project specifications and environmental controls to refine the percentage.
4) When should I include side slope adjustment?
Include it when slopes are dredged rather than vertical cuts, or where templates require flared sides. The option adds a perimeter wedge approximation to better match practical excavation geometry.
5) What is the irregularity factor?
It compensates for uneven seabed, shoals, survey noise, and local pockets. Typical values are 1.02–1.12. Use higher values when the seabed is highly variable or poorly surveyed.
6) How should I handle overdepth?
If the specification allows or requires overdepth, enter the allowance (e.g., 0.30 m) and enable the option. This increases cut depth uniformly and helps align the estimate with payment tolerances.
7) Can I use this for detailed final quantities?
It is best for feasibility, tender, and planning. Final quantities should be derived from hydrographic surveys, design surfaces, and method-specific volume computations approved by the engineer.