Why Do Modern Mines Still Need a Machine That Drills Holes From the Top Down?
Deep underground, where the rock is dark, hard, and unforgiving, mining engineers face a peculiar problem. They need vertical tunnels—called raises or shafts—to move ore, waste, air, and sometimes people between different levels of a mine. For decades, the standard solution was brutal: drill a pattern of holes into the rock face, pack them with explosives, blast, clear the debris, and repeat. It worked. It still works in many places. But it is slow, dangerous, and increasingly difficult to justify when a safer, faster alternative exists.
That alternative is the raise borer, a machine that excavates vertical or inclined shafts without a single stick of dynamite. The raise boring method has quietly become one of the most important mechanical excavation technologies in underground mining, and its adoption continues to grow. According to a comprehensive 2024 review published in Tunnelling and Underground Space Technology, the use of raise boring machines for excavating circular holes between two levels of underground structures “is steadily increasing due to their distinct advantages over traditional drilling and blasting methods”-4. That growth is not a coincidence. It reflects a fundamental shift in how the industry thinks about safety, efficiency, and the economics of underground construction.
To understand why raise boring matters, you first need to understand how it works. The principle is elegantly simple, though the execution is anything but. A raise boring machine operates in two distinct stages. First, a small-diameter pilot hole—typically between 230 and 350 millimeters—is drilled downward from an upper level toward a lower level. This pilot hole is not just a guide; it is the foundation of the entire operation. Its accuracy determines whether the final shaft will end up where the engineers intended. Modern guided drilling rigs can achieve a pilot hole accuracy of about 0.1 meters over 500 meters of depth, a deviation of roughly 0.002 percent-44. That level of precision is remarkable when you consider the scale of the equipment involved and the geological uncertainty of the rock being drilled.
Once the pilot hole breaks through to the lower level, the second stage begins. The pilot bit is removed and replaced with a reamerhead—a large, rotating cutting head that is pulled upward through the pilot hole, enlarging it to its final diameter. This is the part that captures the imagination: a machine pulling a cutterhead the size of a small car through solid rock, grinding it into rubble that falls to the bottom of the shaft and is removed through the lower level. The reaming stage can produce shafts ranging from 0.7 meters to over 6 meters in diameter, and in favorable conditions, depths can exceed 800 meters-. The deepest shaft ever bored using this method reached 1,260 meters with a diameter of 7.10 meters, achieved with machines capable of applying tension forces of approximately 1,600 tons and torques of about 1,100 kNm-44.
But why go to all this trouble? The answer lies in a combination of factors that, taken together, make raise boring compelling for a wide range of applications.
Safety Without Compromise
The most immediate and obvious advantage is safety. Traditional drill-and-blast shaft excavation requires workers to enter the shaft—often a narrow, unsupported vertical opening—to load explosives, inspect conditions, and manage the muck. The Alimak raise climbing method, which has been widely used in underground mining, involves workers ascending and descending a vertical track inside the raise itself. It is a proven method with a reasonable safety record, but it inherently places people in hazardous positions. Raise boring eliminates that exposure almost entirely. The operator sits at a control panel on the upper level, guiding the machine from a safe, stable platform. The rock face where the cutting happens is hundreds of meters away, and no one needs to be near it.
As one technical overview puts it, raise boring “provides a safe means of excavating a shaft between two levels of a mine without the use of explosives”-2. That phrase—without the use of explosives—deserves emphasis. Explosives introduce a whole category of risk: misfires, premature detonation, toxic fumes, and the unpredictable behavior of rock under explosive loading. Raise boring replaces all of that with a controlled, mechanical process that fractures rock through the steady application of force rather than the sudden release of energy.
The Economics of Speed
Safety alone would justify the technology, but raise boring also offers significant economic advantages. A comparison study conducted at the Alpayana Mine in Peru found that raise boring completed a shaft in just 13 days, compared to 28 days using the Alimak method—a productivity improvement of 53 percent-. That kind of time saving translates directly into reduced labor costs, faster project timelines, and earlier access to ore.
The cost picture is more nuanced. In that same Peruvian study, the unit cost of raise boring was $1,048.70 per meter, slightly higher than Alimak’s $1,015 per meter-. But this comparison does not account for the full picture. Raise boring eliminates the need for extensive ground support during excavation, reduces ventilation requirements, and requires fewer personnel. When these factors are included, the total cost advantage often shifts decisively in favor of raise boring. A separate analysis from a Brazilian underground mine found operational cost savings of approximately 64 percent when switching from drill-and-blast to raise boring for a specific application-.
The economics become even more favorable as shaft diameter and depth increase. For large-diameter shafts—say, 4 meters or more—and for deep excavations, raise boring’s efficiency advantages compound. The machine’s ability to maintain consistent penetration rates over long distances means that the per-meter cost decreases with scale, while drill-and-blast methods face diminishing returns due to ventilation constraints, muck removal bottlenecks, and the increasing difficulty of maintaining safe working conditions at depth.
Flexibility in Geometry and Application
Raise boring is not limited to perfectly vertical shafts. The method can excavate raises at angles ranging from horizontal to vertical, giving engineers considerable flexibility in designing underground infrastructure-4. This matters for ventilation shafts, ore passes, waste passes, and even emergency escapeways, each of which may have different geometric requirements.
The technology has found applications well beyond mining. Raise borers have been used in tunneling projects for ventilation shafts, in hydroelectric projects for pressure shafts, and in civil infrastructure for various underground connections-2. The method’s precision and safety profile make it attractive wherever a vertical or steeply inclined opening is needed and the ground conditions are suitable.
When the Ground Fights Back
No technology is without limitations, and raise boring has its share. The method’s effectiveness depends heavily on rock conditions. Very hard and very abrasive rocks increase cutter wear and reduce penetration rates, sometimes to the point where the economics no longer favor raise boring over conventional methods-4. Geological faults, fractured zones, and highly stressed ground can cause problems during both the pilot drilling and reaming stages. A detailed case study from Glencore’s Craig Mine in Sudbury, Ontario—where a 580-meter-long, 3-meter-diameter raise was bored at depths between 1,915 and 2,490 meters—documented six reamer hardware failures during excavation, all attributed to adverse ground conditions and stress-induced spalling around the advancing cutterhead-31.
These challenges are real, but they are also being addressed. Modern raise boring operations incorporate detailed geotechnical assessment, pre-grouting of fractured zones, and careful control of thrust forces and advance rates. The Craig Mine study, for instance, produced a set of best practices for raise boring in highly stressed ground, including minimizing idle time, maintaining face contact, and applying conservative thrust forces with continuous monitoring-31. The industry is learning, and the technology is evolving to handle increasingly difficult conditions.
The Digital Transformation of Raise Boring
One of the most significant recent developments in raise boring is the integration of remote control and automation. Modern raise boring machines can be operated from a remote workstation, where the operator adjusts drilling speed and torque to suit changing ground conditions-. This is not merely a convenience; it is a fundamental improvement in safety and consistency. By removing the operator from the immediate vicinity of the machine, remote control reduces exposure to noise, vibration, and the rare but catastrophic failure modes that can occur during boring operations.
More advanced systems are pushing further. A 2025 industrial application of a raise boring machine with a remote intelligent control system based on 5G communication technology demonstrated autonomous and efficient continuous drilling in complex rock formations with fractured zones-. The system maintained high-precision hole drilling and hole expansion operations, suggesting that fully autonomous raise boring may be closer than many in the industry realize. Semi-automated drive head wrenches and hydraulically powered worktable wrenches, operated remotely, are already making drill string handling faster and safer on modern rigs-.
A Growing Market and a Changing Industry
The market data reflects the technology’s growing prominence. The global raise boring drilling tools market was estimated at approximately $1.4 billion in 2025 and is projected to grow at a compound annual growth rate of 8.6 percent during the forecast period-. The raise boring rig market itself is smaller—projected to reach $400 million by 2032—but its growth rate of 5.8 percent CAGR signals steady demand-. China is the largest market, accounting for roughly 37 percent of global share, followed by Europe at 22 percent and North America at 17 percent-. Major manufacturers include Epiroc, Herrenknecht, and TRB-Raise Borers, with the top five suppliers collectively holding approximately 70 percent of the global market.
This concentration of market share among a few large players reflects the capital-intensive nature of raise boring. A raise boring machine is a significant investment, and the decision to adopt the technology requires careful analysis of project requirements, ground conditions, and long-term operational plans. For mines with multiple shaft projects or ongoing development needs, the investment pays for itself many times over. For one-off projects, the calculus may be different, and conventional methods may remain the more practical choice.
Rethinking Underground Construction
What makes raise boring fascinating is not just the engineering—though the engineering is impressive—but what it represents. It represents a shift in how the industry approaches underground construction. The old model was labor-intensive, explosive-dependent, and inherently hazardous. The new model is mechanized, precise, and increasingly automated. Raise boring is at the forefront of that shift, demonstrating that even in the most difficult environments, there are better ways to build.
The technology is not a panacea. It cannot replace drill-and-blast in every situation, and it faces real technical challenges in difficult ground. But for the right application—a ventilation shaft in competent rock, an ore pass in a deep mine, a pilot hole for a larger excavation—it offers a combination of safety, speed, and precision that conventional methods simply cannot match.
The question, then, is not whether raise boring will continue to grow. The data suggests it will. The question is how quickly the industry will adapt, how effectively the technology will evolve to handle more challenging conditions, and how many of the remaining manual and semi-mechanical shaft excavation operations will eventually be replaced by machines that drill from the top down, safely and efficiently, without a single explosive charge. The answer, based on the trajectory of the past two decades, seems clear. The raise borer is here to stay.