Deep Mine Ventilation Shaft Drilling: CMD100 Retrofits an Aging Datong Mine in 43 Days

Executive Summary

A state-owned legacy mine near Datong, Shanxi Province, had operated for many years at large scale until its ventilation system deteriorated badly: airflow capacity was insufficient, gas concentrations persistently exceeded limits, and a new deep, large-diameter ventilation shaft became a direct safety requirement. The ground was hard and highly abrasive, with local fractured zones and collapse-prone intervals that had repeatedly caused wall collapse and stuck-pipe incidents on earlier attempts. The CORTECH® CMD100 full-hydraulic truck-mounted rig, fitted with a large-diameter high-pressure DTH (down-the-hole) hammer and a pneumatic DTH drilling program, executed a multi-diameter sequence — Φ350 mm opening, cased surface section, Φ254 mm DTH run to the target roadway, then staged reaming to a final Φ500 mm — and completed the shaft in 43 days at a final depth of 303 m. The finished wall was stable and vertical, ventilation capacity met the safety design, and the gas-explosion risk was materially reduced.

Project Background & Challenge

Decades of mining had left the operation in a difficult position:

• Ailing ventilation, gas over-limit: years of large-scale extraction degraded the ventilation network, and gas concentrations kept exceeding limits — a major hazard to underground personnel.
• Hard, abrasive, fractured rock: the formation was hard and abrasive, with local broken zones and easy-collapse sections.
• Conventional rigs kept failing: ordinary rigs were slow, expensive and repeatedly suffered wall collapse and stuck pipe, missing schedule and blocking the mine's safety program.

Our Solution

After site survey and engineering review, the team chose the CMD100 with a high-pressure pneumatic DTH program:

• Opening and surface casing: the bore was opened at Φ350 mm; once the surface section was finished, casing was run immediately to stabilize the wall and prevent collapse.
• DTH run to the roadway: a Φ254 mm DTH hammer then drilled ahead through the hard abrasive rock to the planned roadway intersection.
• Staged reaming to diameter: the hole was reamed in steps to the finished Φ500 mm, with strict control of wall stability and bore verticality throughout.
• Rig enablers: the CMD100's 100 t (1,000 kN) pullback, 27,500 Nm low-speed torque and 559 kW Cummins engine delivered the force to push DTH tools through abrasive rock; its 20.6 MPa integrated air/mud manifold supports high-volume pneumatic DTH circulation, and six outriggers held alignment steady.

Key Results

For the full technical specifications of the CORTECH® CMD100, see the CMD100 product page.

Customer Value & ROI

• Safety case closed: the new shaft restored ventilation capacity to design and materially cut gas-explosion risk for the mine's workforce.
• No repeat incidents: the casing-then-DTH-then-reaming sequence avoided the collapse and stuck-pipe events that had stalled previous contractors, protecting schedule and budget.
• Precision at depth: controlled verticality meant the bore intercepted the planned roadway accurately — essential for a ventilation connection between surface and underground workings.
• Recognition earned: the on-time, stable-hole result was highly commended by the owner and supports the mine's safety-standardization program.

FAQ

How do you drill a ventilation shaft for an old mine?

A proven retrofit sequence is to open a generous surface hole (here Φ350 mm), case the unstable surface section, then drill a DTH pilot (Φ254 mm) through hard rock to the target roadway, and finally ream in steps to the finished diameter (Φ500 mm) while controlling verticality.

What diameter program is used for a 300 m ventilation shaft?

This 303 m shaft used a Φ350 mm opening, a cased surface section, a Φ254 mm DTH pilot to the roadway, and staged reaming to a finished Φ500 mm.

Which rig drills hard, abrasive rock to precise verticality?

The CMD100's 100 t pullback, 27,500 Nm low-speed torque, high-pressure pneumatic DTH circulation (20.6 MPa manifold) and six-point outriggers deliver the push and stability needed to hold alignment in abrasive, fractured rock.

How long does a deep mine ventilation retrofit take?

This 303 m, Φ500 mm ventilation shaft for an aging Datong mine was completed in 43 days, including casing, DTH drilling and staged reaming.

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