1. Typical drilling time (per hole)
Surrounding rock classRock conditionAverage penetration rateTime for 4.5 m hole
Class II–IIIHard / medium-hard rock0.8–1.2 m/min4–6 minutes
Class IVMedium to soft rock1.2–1.8 m/min2.5–4 minutes
Class VVery soft / fractured rock1.8–2.5 m/min2–3 minutes
👉 Most tunnel projects estimate about 3–5 minutes per 4.5 m hole under normal conditions.
2. Factors that affect drilling time
Rock drilling jumbo type
Modern hydraulic jumbo (single or double arm): faster and more stable
High-frequency drifter: higher penetration rate
Rock drill parameters
Impact power
Rotation speed
Feed force
Bit diameter (usually 38–45 mm for anchor holes)
Rock conditions
Quartz content
Fractures and joints
Water inflow
Auxiliary time (not pure drilling)
Positioning the boom
Hole alignment and correction
Rod connection / withdrawal
3. Practical construction reference
In tunnel support construction using a single-arm rock drilling jumbo:
Pure drilling time: ~3–5 min per hole
Total cycle time per hole (including positioning): ~6–8 min
This is why a jumbo can typically complete 60–100 anchor holes per shift, depending on layout and rock conditions.
If you'd like, we can also:
Estimate daily drilling capacity for your tunnel size
Compare single-arm vs double-arm jumbo efficiency
Recommend drill parameters for Class II surrounding rock
Just tell us your tunnel section size and rock class.
