Enter Project Inputs
Example Data Table
Use this sample to understand typical tunnel segment takeoff inputs and outputs.
| Input | Value | Notes |
|---|---|---|
| Tunnel internal diameter | 6.00 m | Clear inside diameter |
| Segment thickness | 0.30 m | Typical precast segment |
| Ring width | 1.50 m | Axial length per ring |
| Tunnel length | 300 m | Total lined length |
| Segments per ring | 8 | Includes key segments if applicable |
| Spares percentage | 2% | Damage and handling buffer |
Formula Used
Ro = Ri + Thickness
Vring = π × (Ro² − Ri²) × Ring Width
Vtotal = Vring × Rings
Spares = ceil( Segments(base) × Spares% )
Segments(total) = Segments(base) + Spares
Vgrout = π × (Re² − Ro²) × Ring Width × Rings
Vgrout(adj) = Vgrout × (1 + Loss%)
Gasket = 2π × (Ri + Thickness/2) × Rings × (1 + Waste%)
How to Use This Calculator
- Select the input unit and enter tunnel geometry values.
- Provide segments per ring and an allowance for spares.
- Enter excavation diameter to estimate grout volume.
- Add grout loss and gasket waste to match site practices.
- Click Calculate to view results above the form.
- Use Download CSV or Download PDF for takeoffs.
For final designs, confirm segment drawings, joint details, and ring build tolerances.
Segment Lining Quantity Planning Guide
1) What the Takeoff Represents
This calculator converts tunnel geometry into ring counts and segment quantities for preliminary procurement. A ring is treated as a full 360° lining unit. The outputs estimate total segments, concrete volume, lining weight, gasket length, and annulus grout volume for a drive section.
2) Key Inputs and Typical Ranges
Segment internal diameter often ranges from 2 m to 12 m for utility and transit tunnels. Ring width is commonly 1.2 m to 2.0 m, depending on the TBM and handling limits. Segments per ring typically fall between 5 and 8. Many projects start with 2% to 5% spares and refine after early rings.
3) Procurement Quantities You Can Derive
Total segments equal rings multiplied by segments per ring, then adjusted by spares. Concrete volume is calculated using annulus area (outer radius squared minus inner radius squared) times ring width and ring count. Using a nominal reinforced concrete density near 2400 kg/m³, you can approximate handling weight for lifting plans and transport capacity.
4) Grout and Gasket Allowances
Backfill grout volume is estimated from the difference between excavation diameter and segment outer diameter. Field grout losses vary with ground conditions, overcut, and injection control; 3% to 15% is a practical planning band. Gasket length is taken as the circumference at the gasket line per ring, then adjusted for waste; 1% to 3% suits early budgeting.
5) How to Use Results on Site
Use the segment totals to schedule casting, curing, and deliveries by week, and cross-check against TBM advance rates. Compare grout estimates to batch plant capacity and delivery cycle times. When as-built data becomes available, update spares and loss factors to align the forecast with actual consumption. Record ring build notes to justify revisions in procurement forecasts.
FAQs
1) What if my ring uses different segment types?
Calculate the total segments per ring, then split the result by type using your ring drawing ratios. Keep spares by type, especially for key and taper segments.
2) How should I choose a spares percentage?
Start with 2%–5% for planning. Increase for long drives, difficult handling, or high breakage risk, then reduce once damage rates are confirmed.
3) Does the calculator include taper rings or curve packs?
No. Add special rings separately based on alignment geometry and the supplier’s ring schedule, then combine with the straight-ring quantities.
4) Why is grout based on excavation diameter?
Grout fills the annular gap between the excavated bore and the segment outer diameter. Overcut, ground loss, and steering can increase the real volume.
5) What density should I use for lining weight?
For reinforced concrete, 2400 kg/m³ is a common estimate. Confirm with mix design and rebar percentage for lifting and transport checks.
6) How do I handle unit conversions?
Select your unit system at the top. The calculator converts to a consistent internal basis before computing volumes, weights, and lengths.
7) Can I use these results for final payment quantities?
Use them for budgeting and early takeoff. Final quantities should follow contract measurement rules and verified as-built ring records.