TBM Advance Rate Calculator

Inputs

Project length (m) *

Shift hours (h) *

Shifts per day *

Working days per month *

Penetration rate value *

Typical ranges vary by geology and cutter condition.

Penetration rate unit

Utilization factor (%) *

Captures minor stops not logged as downtime.

Downtime breakdown (minutes per day)

These reduce effective boring time in Method A.

Maintenance

Lining / Segment erection

Method B models this via ring build time.

Survey / Guidance

Mucking / Conveyance delays

Shift change / Handover

Other delays

Optional cycle inputs (Method B)

Used for ring-by-ring modeling per meter.

Ring length (m)

Ring build time (min/ring)

Extra delays (min/m)

Add for logistics, QC, or frequent short stops.

Clear Results

Formula used

Method A: Time-available model

Total_minutes = shift_hours × shifts_per_day × 60
Downtime_total = Σ(downtime categories)
Effective_minutes = max(0, Total_minutes − Downtime_total)
Net_boring_minutes = Effective_minutes × (Utilization% / 100)
Advance_day = Penetration(m/min) × Net_boring_minutes

This method works best when you can estimate daily downtime totals from shift logs.

Method B: Cycle model per meter (optional)

Boring_min_per_m = 1 / Penetration(m/min)
Lining_min_per_m = Ring_build_min / Ring_length_m
Cycle_min_per_m = Boring + Lining + Extra_delay
Net_minutes = (Total_minutes − Fixed_downtime_excluding_lining) × (Utilization%/100)
Advance_day = Net_minutes / Cycle_min_per_m

This method avoids double-counting when lining time is modeled via ring cycles.

How to use this calculator

Enter scheduled shifts, shift hours, and working days per month.
Input penetration rate and choose the correct unit.
Add downtime by category using your typical daily averages.
Set utilization to reflect minor stops and variability.
Optionally enter ring length and ring build time for Method B.
Click Calculate to view results above the form.
Use CSV or PDF export for reporting and scenario comparison.

Example data table

Scenario	Penetration	Utilization	Total downtime	Advance (m/day)	Notes
Baseline	60 mm/min	70%	495 min/day	37.8	Typical multi-shift operation
Improved logistics	60 mm/min	75%	420 min/day	48.6	Reduced delays and better handover
Harder ground	40 mm/min	70%	495 min/day	25.2	Lower penetration dominates output

Example figures are illustrative. Use site data for planning decisions.

Practical guide to TBM advance rate planning

1) Purpose and scope

This calculator converts field assumptions into a daily and monthly advance forecast for a tunnel boring machine (TBM). It combines scheduled time, downtime, and penetration performance to estimate production and a rough completion duration. Results support shift planning, target-setting, and scenario comparison across geology or operating strategies.

2) Key inputs and typical ranges

Penetration is entered as mm/min or m/hr. In many projects, hard rock conditions may trend lower (e.g., 20–60 mm/min), while favorable conditions can trend higher (e.g., 60–120 mm/min), depending on cutter wear, thrust, and ground behavior. Utilization typically ranges 55–85% and should reflect frequent short stops not captured as “downtime.”

3) Downtime categorization and data quality

Downtime is entered in minutes per day by category such as maintenance, lining, survey, and mucking. Use rolling averages from logs (for example, 30-day means) rather than best-day performance. If total downtime approaches available time, the model correctly drives production toward zero, signaling unrealistic assumptions.

4) Reading Method A vs Method B

Method A applies downtime totals directly and is ideal when you already track daily delay minutes. Method B introduces a per-meter cycle using ring length and ring build time, then allocates available minutes to that cycle. Method B is helpful for lining-dominated drives and avoids double-counting if lining is modeled through ring cycles.

5) Worked example and interpretation

Suppose 3 shifts/day × 8 h/shift gives 1,440 min/day. If downtime totals 495 min/day and utilization is 70%, net boring minutes become (1,440 − 495) × 0.70 = 661.5 min/day. With 60 mm/min (0.06 m/min), Method A yields 0.06 × 661.5 ≈ 39.7 m/day, which is about 1,032 m/month at 26 working days. Compare scenarios by adjusting utilization and the largest downtime drivers first.

FAQs

1) What is the difference between penetration rate and advance rate?

Penetration describes cutting speed while boring, such as mm/min. Advance rate is delivered progress over time, such as m/day, after downtime and utilization reduce available boring minutes.

2) What utilization value should I use?

Use a realistic average from logs. Many drives fall between 55% and 85%. If downtime already includes every short stop, use a higher utilization; otherwise keep it conservative.

3) Why does downtime exceed available minutes?

It usually indicates double counting or mismatched bases, such as per-shift delays entered as per-day values. Align all downtime values to minutes per day before calculating.

4) When should I rely on Method B?

Use Method B when segment erection or ring build time drives production, and you have credible ring length and build-time data. It models lining per meter rather than as a daily lump sum.

5) Can I model learning curves or improved performance over time?

Yes. Run monthly scenarios with updated penetration, downtime, and utilization assumptions. Export results and compare phases such as startup, steady-state, and maintenance-heavy periods.

6) Does this estimate include geological risk and stoppages?

Not explicitly. Add risk allowances by increasing downtime or reducing penetration/utilization. For major risks like faults or water inflow, plan separate contingency windows outside the model.

7) Why is my monthly production high but completion days seem low?

Check that project length is in meters and working days per month matches your schedule. Also verify penetration units; mm/min entered as m/hr can inflate advance significantly.