Large Diameter Ventilation Shaft Drilling: CMD130 Builds Φ710 mm × 920 m in 32 Days

Executive Summary

A deep underground mine in Shandong Province, China, faced a deteriorating ventilation network as mining depth increased: shaft resistance rose, intake airflow fell short of safety requirements, and a large-diameter deep ventilation shaft had to be delivered quickly. The target formation was deeply buried, hard rock with well-developed fractures, where conventional rigs were slow and prone to hole problems. The CORTECH® CMD130 truck-mounted large-diameter drilling rig, fitted with large-diameter cluster DTH (down-the-hole) hammers and a staged reaming process, completed a Φ710 mm diameter, 920 m-deep ventilation shaft in 32 days. Construction quality was rated excellent and the delivered ventilation capacity fully met the mine's design requirements, establishing a proven template for similar deep-mine ventilation projects.

Project Background & Challenge

As the mine deepened, three problems compounded into an urgent safety case:

• High resistance, insufficient air: underground ventilation resistance climbed with depth and air volume fell below the safety requirement, directly threatening the working environment.
• Hard, fractured ground: the formation sat at great overburden depth, with high rock hardness and well-developed fractures — conditions that punish low-torque rigs and make borehole stability a constant risk.
• Conventional methods too slow: ordinary rigs offered low penetration and long schedules, which the mine could not accept given the active safety exposure.

Our Solution

We selected the CMD130 truck-mounted rig with cluster DTH hammers and a staged reaming process tailored to deep hard rock:

• 130 t pullback, deep-hole muscle: 130 t (1,300 kN) hoisting pullback and 26 t (260 kN) pulldown safely handled the large-diameter tool string and casings all the way to 920 m.
• High-torque hard-rock drilling: the upper-deck Chongqing Cummins QSK19-C760 engine (567 kW @ 2,100 rpm) delivered a continuous 31,000 Nm of breakdown torque at up to 300 rpm — exactly what hard, fractured rock demands.
• Large-diameter capacity: an 820 mm maximum drilling diameter and 21.2 m telescopic mast supported the Φ710 m finished shaft in a single reaming campaign.
• Fast, crane-free mobilization: the 10×8 heavy truck chassis carries a legal road weight of 54.5 t, so the rig drove itself to site and set up with six hydraulic outriggers instead of a heavy-haul and crane crew.
• Staged reaming in fractured ground: cluster DTH hammers, supported by a 35 MPa integrated air/mud manifold, reamed the hole in controlled steps and kept the bore clean through fractured zones.

Key Results

For the full technical specifications of the CORTECH® CMD130, see the CMD130 product page.

Customer Value & ROI

• Safety restored on schedule: the 920 m shaft was delivered in 32 days, ending the air-shortage exposure that had restricted the mine's working environment.
• No heavy-logistics premium: because the rig self-mobilized on its 10×8 chassis, the mine avoided heavy-haul trucks, lowboys and crane setup costs normally attached to a 130 t-class rig.
• Hole integrity in fractured rock: staged reaming and the high-torque DTH setup kept the bore stable through developed fractures, minimizing collapse-related downtime.
• Replicable template: the project matured a repeatable method for deep, hard-rock ventilation shafts — directly transferable to comparable mines.

FAQ

How deep can a large diameter ventilation shaft drilling rig go?

In this project the CORTECH CMD130 drilled and reamed a finished Φ710 mm ventilation shaft to 920 m. With 130 t (1,300 kN) pullback and a 567 kW / 31,000 Nm top drive, the rig is engineered for deep, large-diameter shafts well beyond this application.

What is staged reaming for a ventilation shaft?

Staged reaming drills a smaller pilot opening first, then enlarges the bore in controlled steps using progressively larger DTH hammers. It reduces the power needed for each pass, stabilizes fractured ground and delivers a smooth, gauge wall — the method used here through hard, fractured rock to 920 m.

Which rig drills a Φ710 mm ventilation shaft in hard fractured rock?

A high-torque, truck-mounted large-diameter rig such as the CMD130 (31,000 Nm breakdown torque, 820 mm max opening diameter, 130 t pullback) is purpose-built for this combination of hard rock, large diameter and deep overburden.

How long does a 900 m ventilation shaft take to drill?

This Φ710 mm × 920 m shaft was completed in 32 days with the CMD130 and cluster DTH staged reaming, including setup and hole cleaning — a schedule driven by the rig's mobility and hard-rock penetration rather than by conventional slow rotary methods.

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